LOOMIS SAYLES HIGH INCOME FUND

Supplement dated September 24, 2008 to the Loomis Sayles High Income Fund Class Y Prospectus dated September 15, 2008, as may be revised or supplemented from time to time.

Effective immediately, the following text is added to the sub-section “Principal Investment Strategies” under the section “Goals, Strategies & Risks” with respect to the Fund:

The Fund may also invest in swaps (including credit default swaps) and other derivatives.

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Effective immediately, the following bullet describing the valuation of credit default swaps is added to the sub-section “How Fund Shares Are Priced” under the section “Fund Services”:

• Credit default swaps – dollar prices supplied by a pricing service for such securities, if available. If prices from a pricing service are unavailable, such securities shall be priced using spread levels based on bid or spread quotations obtained from two or more broker-dealers that are believed to follow the issue.

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Effective immediately, the following paragraph is added to the section “Glossary of Terms:”

Swap agreements – Swap agreements are unregulated, individually negotiated contracts between two parties who agree to exchange for a specified period of time two streams of payments that would be earned or realized on particular notional investments or instruments. In a credit default swap, one party agrees to make periodic payments to a counterparty, in exchange for the right to receive a payment in the event of default of the underlying reference security.

LOOMIS SAYLES HIGH INCOME FUND

Supplement dated September 24, 2008 to the Natixis Funds Statement of Additional Information – Part II dated September 15, 2008, as may be revised or supplemented from time to time.

Effective immediately, the following text is inserted immediately following the fifteenth paragraph under the sub-section “Options” under the section “Investment Strategies and Risks; Types of Practices:”

Swap Agreements

Certain Funds may enter into a variety of swap agreements, including but not limited to interest rate, index, commodity, equity linked, credit default, credit linked and currency exchange swaps. Depending on the structure of the swap agreement, a Fund may enter into swap transactions to preserve a return or spread on a particular investment or portion of its portfolio, to gain exposure to one or more securities, currencies, commodities, or interest rates, to protect against or attempt to take advantage of currency fluctuations, to protect against any increase in the price of securities that the Fund anticipates purchasing at a later date, to efficiently gain exposure to certain markets, or to shift a Fund’s investment exposure from one type of investment to another.

Swap agreements are unregulated, individually negotiated contracts between two parties who agree to exchange for a specified period of time two streams of payments that would be earned or realized on particular notional investments or instruments. In a typical interest rate swap, for example, one party agrees to make regular payments equal to a floating interest rate times a “notional principal amount,” in return for payments equal to a fixed rate times the same amount, for the term of the swap agreement. The “notional principal amount” of a swap transaction is the agreed upon basis for calculating the payments that the parties agree to exchange, i.e., the return on or increase in value of a particular dollar amount invested at particular interest rate, in a particular foreign currency or commodity, or in a “basket” of securities. Under most swap agreements, payments by the parties will be exchanged on a “net basis,” and a party will receive or pay, as the case may be, only the net amount of the two payments. A Fund will designate assets in an amount sufficient to cover its current net obligations under swap agreements.

Swap agreements are sophisticated hedging instruments that typically involve a small investment of cash relative to the magnitude of risks assumed. Swaps can be highly volatile and may have a considerable impact on a Fund’s performance, as the potential gain or loss on any swap transaction is not subject to any fixed limit. A Fund’s successful use of swap agreements will depend on the Advisor’s ability to predict correctly whether certain types of investments are likely to produce greater returns than other investments. Even though swap markets in which swap transactions are traded have grown exponentially in recent years, swap agreements are typically not traded on exchanges and are subject to liquidity risk. As a result, a Fund bears the risk of loss of the amount expected to be received pursuant to a swap agreement in the event of the default or bankruptcy of the counterparty, and the value of a swap agreement in general depends on the creditworthiness of the counterparty. A Fund may also suffer losses if it is unable to terminate (or terminate at the time and price desired) outstanding swap agreements (either by assignment or other disposition) or reduce its exposure through offsetting transactions.

Credit Default Swaps

Certain Funds may enter into credit default swap agreements, which may have as reference obligations one or more debt securities or an index of such securities. In a credit default swap, one party (the “protection buyer”) is obligated to pay the other party (the “protection seller”) a stream of payments over the term of the contract, provided that no credit event, such as a default or a downgrade in credit-rating, occurs on the reference obligation. If a credit event occurs, the protection seller must generally pay the protection buyer the “par value” (the agreed upon notional value) of the referenced debt obligation in exchange for an equal face amount of deliverable reference obligations.

A Fund may be either the protection buyer or protection seller in a credit default swap. If a Fund is a protection buyer, such Fund would pay the counterparty a periodic stream of payments over the term of the contract and would not recover any of those payments if no credit event were to occur. However, if a credit event occurs, a Fund that is a protection buyer has the right to deliver the referenced debt obligations and receive the par value of such debt obligations from the counterparty protection seller. As a protection seller, a Fund would receive fixed payments throughout the term of the contract if no credit event occurs. If a credit event occurs, however, the value of the obligation received by the Fund (e.g., bonds which defaulted), plus the periodic payments previously received, may be less than the par value of the obligation, resulting in a loss to the protection seller. Furthermore, a Fund that is a protection seller would effectively add leverage to its portfolio because such Fund will have investment exposure to the notional amount of the swap. A Fund may not enter into any credit default swaps, other than for hedging purposes, if at the time it enters into the swap the aggregate notional value of all then outstanding credit default swaps entered into by the Fund for non-hedging purposes exceeds 20% of the Fund’s total assets.

Credit default swap agreements are subject to greater risk than a direct investment in the reference obligation. Like all swap agreements, credit default swaps are subject to liquidity, credit and counterparty risks. See “Swap Agreements” above. In addition, collateral posting requirements are individually negotiated and there is no regulatory requirement that a counterparty post collateral to secure its obligations under a credit default swap. Furthermore, there is no requirement that a party be informed in advance when a credit default swap agreement is sold. Accordingly, a Fund may have difficulty identifying the party responsible for payment of its claims. The notional value of credit default swaps with respect to a particular investment is often larger than the total par value of such investment outstanding and, in event of a default, there may be difficulties in making the required deliveries of the reference investments, possibly delaying payments.

The market for credit default swaps has become more volatile recently as the creditworthiness of certain counterparties has been questioned and/or downgraded. If a counterparty’s credit becomes significantly impaired, multiple requests for collateral posting in a short period of time could increase the risk that the Fund may not receive adequate collateral. There is no readily available market for trading credit default swaps. The Fund generally may exit its obligations under a credit default swap only by terminating the contract and paying applicable breakage fees, or by entering into an offsetting credit default swap position, which may cause the Fund to incur more losses.

Investment Pools of Swap Contracts

Certain Funds may invest in publicly or privately issued interests in investment pools whose underlying assets are credit default, credit linked, interest rate, currency exchange, equity linked or other types of swap contracts and related underlying securities or securities loan agreements. The pools’ investment results may be designed to correspond generally to the performance of a specified securities index or “basket” of securities, or sometimes a single security. These types of pools are often used to gain exposure to multiple securities with less of an investment than would be required to invest directly in the individual securities. They may also be used to gain exposure to foreign securities markets without investing in the foreign securities themselves and/or the relevant foreign market. To the extent that a Fund invests in pools of swap contracts and related underlying securities whose performance corresponds to the performance of a foreign securities index or one or more of foreign securities, investing in such pools will involve risks similar to the risks of investing in foreign securities. In addition to the risks associated with investing in swaps generally, an investing Fund bears the risks and costs generally associated with investing in pooled investment vehicles, such as paying the fees and expenses of the pool and the risk that the pool or the operator of the pool may default on its obligations to the holder of interests in the pool, such as the Fund. Interests in privately offered investment pools of swap contracts may be considered illiquid and, except to the extent that such interests are issued under Rule 144A and deemed liquid, subject to a Fund’s restriction on investments in illiquid securities.