1. In the insect Leucophaea maderae the incidence of tumors developing after severance of the recurrent nerve is high—i.e., roughly 75 per cent. The incidence does not seem to differ significantly in males and females. Accordingly, castrates respond to the nerve transection in approximately the same way as noncastrate animals. Among the organs involved tumors appear most frequently in the midgut (stomach), an observation which may perhaps be explained by a more rapid and more destructive growth pattern of these as compared to tumors in other sites (salivary organs, foregut).

  2. The mortality rates of tumor-bearing animals differ significantly: males as a group survive longer than females. The sex difference in resistance to the presence of tumors disappears after castration. This observation offers indirect evidence, but no proof, for the presence of sex hormones in insects.

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Research grants from the American Cancer Society and The Anna Fuller Fund are gratefully acknowledged.

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