The investment objective of the Fund is to provide long-term total return, comprised primarily of capital appreciation.

These tables summarize the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.

The Fund invests principally in equity securities (such as common stock) issued by small-to-medium capitalization U.S. companies. The Fund employs a “core equity” investment strategy that seeks to meet the Fund’s investment objective by investing in both growth- and value-oriented equity securities. Under normal circumstances, the Fund will invest at least 80% of its net assets (plus borrowings for investment purposes, if any) in the equity securities of small-to-medium capitalization U.S. companies. (If the Fund changes this investment policy, the Fund will notify shareholders at least 60 days in advance of the change.) For purposes of the 80% test, equity securities include securities such as common stock, preferred stock, and other securities that are not debt securities, cash or cash equivalents. For purposes of this investment policy, the Fund considers “small to medium capitalization U.S. companies” to be U.S. companies with market capitalizations between $25 million and the largest company included in the Russell 2500^® Index (as of June 30, 2026, $23.9 billion). The Fund may invest in derivative instruments, such as exchange-listed equity futures contracts, to gain market exposure on cash balances or to reduce market exposure in anticipation of liquidity needs. Investments in derivatives may be applied toward meeting a requirement to invest in a particular kind of investment if the derivatives have economic characteristics similar to that investment.

In addition, certain subadvisers may employ a quantitative investment process in seeking to achieve the Fund’s investment objective.

The following bar chart and table give some indication of the risks of investing in the Fund by showing changes in the performance of the Fund’s Class Y-3 shares from year to year and comparing the Fund’s average annual returns over time with a broad-based securities market index, the Russell 2500^® Index.

The Fund offers four different classes of shares in this prospectus: Adviser Class shares, Class I shares, Class Y-2 shares and Class Y-3 shares. No information is shown for Adviser Class or Class Y-2 shares because there were no shares outstanding for these classes as of the last calendar year end. Performance information for these share classes will appear in a future version of the prospectus once there is a full calendar year of performance information to report. The returns of these share classes would have been substantially similar to the returns of Class Y-3 shares; however, because the Adviser Class, Class I and Class Y-2 shares are subject to a 12b-1 fee and/or a non-distribution shareholder administrative services fee, the returns of these share classes would have been lower than those shown for Class Y-3 shares.

The Fund’s past performance, before and after taxes, is not necessarily an indication of how the Fund will perform in the future. This may be particularly true given that other subadvisers were responsible for managing portions of the Fund’s portfolio during previous periods. Westfield Capital Management Company, L.P. assumed responsibility for managing a portion of the Fund’s portfolio on August 15, 2005. Parametric Portfolio Associates LLC assumed responsibility for managing a portion of the Fund’s portfolio on February 25, 2015. Effective June 27, 2016, the Fund changed certain of its subadvisers and revised its principal investment strategies. For periods prior to June 27, 2016, the Fund’s past performance in the bar chart and table reflects the Fund’s prior subadviser lineup and principal investment strategies. GW&K Investment Management, LLC, Loomis, Sayles & Company, L.P. and LSV Asset Management each assumed responsibility for managing a portion of the Fund’s portfolio on July 1, 2016. River Road Asset Management, LLC assumed responsibility for managing a portion of the Fund’s portfolio on April 30, 2019.

The Fund’s calendar year-to-date return as of June 30, 2026 was 18.20%.

The Fund’s highest return for a quarter during the periods shown above was 26.07%, for the quarter ended June 30, 2020.

The Fund’s lowest return for a quarter during the periods shown above was -30.23%, for the quarter ended March 31, 2020.

After-tax returns are calculated using the historical highest individual federal marginal income tax rates in effect and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s situation and may differ from those shown. In addition, the after-tax returns shown are not relevant to investors who hold Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. In some cases, the after-tax returns may exceed the return before taxes due to an assumed benefit from any losses on a sale of shares at the end of the measurement period. After-tax returns are shown for Class Y-3 shares. After-tax returns for Class I shares may vary.

Equity Securities Risk. The value of a company’s equity securities is subject to changes in the company’s financial condition, and overall market and economic conditions. U.S. and global stock markets have experienced periods of substantial price volatility in the past and may do so in the future.

Issuer Risk. The issuer of a security may perform poorly and the value of its stocks or bonds may decline as a result. An issuer of securities held by the Fund could become bankrupt or could default on its issued debt or have its credit rating downgraded.

Real Estate Investment Trusts (“REITs”) Risk. REITs may be affected by changes in the value of the underlying properties owned by the trusts and by the quality of any credit extended. Further, REITs are dependent upon specialized management skills and cash flows, and may have their investments in relatively few properties, or in a small geographic area or a single property type. Failure of a company to qualify as a REIT under federal tax law may have adverse consequences to the Fund. In addition, to the extent that the Fund invests in REITs, the Fund must bear the REIT’s expenses in addition to the expenses of its own operation and is subject to risks associated with extended vacancies of properties or defaults by borrowers or tenants, particularly during periods of disruptions to business operations or an economic downturn.

Growth Stock Risk. The value of a company’s equity securities is subject to changes in the company’s financial condition, and overall market and economic conditions. Companies with strong growth potential (both domestic and foreign) tend to have higher than average price-to-earnings ratios, meaning that these stocks are more expensive than average relative to the companies’ earnings. The market prices of equity securities of growth companies are often quite volatile, since the prices may be particularly sensitive to economic, market, or company developments and may present a greater degree of risk of loss.

Derivatives Risk. The Fund may engage in a variety of transactions involving derivatives, such as options, futures, forwards and swap agreements. Derivatives are financial instruments, the values of which depend upon, or are derived from, the value of something else, such as one or more underlying investments, pools of investments, indices, or currencies. A subadviser may use derivatives both for hedging and non-hedging purposes, although it is anticipated that the use of derivatives by the Fund will generally be limited to maintaining exposure to certain market segments or asset classes, increasing or decreasing currency exposure, or facilitating certain portfolio transactions. A subadviser may also use derivatives such as exchange-listed equity futures contracts, swaps and currency forwards to equitize cash held in the portfolio. Investments in derivatives may be applied toward meeting a requirement to invest in a particular kind of investment if the derivatives have economic characteristics similar to that investment.

Derivatives involve special risks and may result in losses. The successful use of derivatives depends on the ability of a subadviser to manage these sophisticated instruments. The prices of derivatives may move in unexpected ways due to the use of leverage or other factors, especially in unusual market conditions, and may result in increased volatility of the Fund’s share price. Certain derivatives are subject to counterparty risk, which is the risk that the other party to the transaction will not fulfill its contractual obligations, and risks arising from margin requirements, which include the risk that the Fund will be required to pay additional margin or set aside additional collateral to maintain open derivative positions. Certain derivatives are subject to mandatory central clearing and exchange-trading. Central clearing is intended to reduce counterparty credit risk, but central clearing does not make derivatives transactions risk-free Exchange-trading is intended to increase liquidity, but there is no guarantee the Fund could consider exchange-traded derivatives to be liquid. Some derivatives are more sensitive to interest rate changes and market movements than other instruments. The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.

Certain derivative instruments provide the economic effect of financial leverage by creating additional investment exposure, as well as the potential for greater loss. If a subadviser uses leverage through purchasing derivative instruments, the Fund has the risk of capital losses that exceed the net assets of the allocable portion of the Fund managed by that subadviser. The net asset value of the Fund employing leverage will be more volatile and sensitive to market movements. Leverage may involve the creation of a liability that requires the Fund to pay interest.

Derivatives instruments may also be susceptible to operational risks. Failures in the documentation and shortcomings in the settlement process could result in the failure to complete a transaction. There are also legal risks associated with derivatives, particularly if contracts are not legally enforceable or if a counterparty does not have sufficient capacity to perform on a contract.

Quantitative Model Risk. One or more subadvisers to the Fund follows a quantitative model strategy to manage its allocated portion of the Fund. Quantitative models (both proprietary models developed by a quantitative-focused subadviser, and those supplied by third parties) and information and data supplied by third parties can be incorrect, misleading or incomplete, and any decisions made in reliance thereon can expose the Fund to potential risks of loss. In addition, the use of predictive models can also expose the Fund to potential risks of loss. For example, such models may incorrectly forecast future behavior, leading to potential losses on a cash flow and/or a mark-to-market basis. In addition, in unforeseen or certain low-probability scenarios (often involving a market disruption of some kind), such models may produce unexpected results, which can result in losses for the Fund.

If the assumptions made by quantitative-focused subadvisers in their underlying models are unrealistic, inaccurate or become unrealistic or inaccurate and are not promptly adjusted to account for changes in the overall market environment, it is likely that profitable trading signals will not be generated. If and to the extent that the models do not reflect certain factors, and a quantitative-focused subadviser does not successfully address such omission through its testing and evaluation, and modify the models accordingly, the Fund may experience losses. In addition, because of the complexity of quantitative-focused investment strategy programming and modeling, there is a risk that the finished model may contain an error; one or more of such errors could adversely affect the Fund’s performance.

To the extent that a quantitative-focused subadviser is not able to develop sufficiently differentiated models, the Fund’s investment objective may not be met, irrespective of whether the models are profitable in an absolute sense, as a result of “crowding” or “convergence” of the model’s output with actions taken by other market participants. In addition, to the extent a quantitative subadviser’s model focuses on identifying a certain type of stock (e.g., high relative profitability stocks), those stocks may perform differently from the market as a whole, which could cause the Fund to underperform.

The models and proprietary research of a quantitative subadviser are largely protected by the subadviser through the use of policies, procedures, agreements, and similar measures designed to create and enforce robust confidentiality, non-disclosure, and similar safeguards. However, aggressive position-level public disclosure obligations (or disclosure obligations to exchanges or regulators with insufficient privacy safeguards) could lead to opportunities for competitors to reverse-engineer a subadviser’s models and data, and thereby impair the relative or absolute performance of the Fund.

Sector Risk. While the Fund does not have a principal investment strategy to focus its investments in any particular sector, the Fund from time to time may have significant exposure to one or more sectors, such as consumer (non-cyclical and cyclical), financials and industrials. The Fund may have little or no exposure to certain other sectors. There are risks associated with having significantly overweight or underweight allocations to certain sectors, such as that an individual sector may be more volatile than the broader market, or could perform differently, and that the stocks of multiple companies within a sector could simultaneously rise or decline in price because of, for example, investor perceptions, an event that affects the entire sector or other factors.