Peripheral nerve and regeneration in Crustacea.

There is now good evidence that in the Vertebrata peripheral nerves exert an important trophic effect on the regeneration of the structures which they innervate (Millot, 1931; Needham, J. 1942; Hamburger, 1944). In invertebrates the nervous system is not always necessary; Millot (1931, p. 117) concluded that in types where regenerative powers are comparatively limited (e.g. Mollusca, some Nemertinea), the nervous system is necessary, while in types with extensive regenerative powers (Tunicata, many Platyhelmia) it may be unnecessary. Some of the Crustacea are outstanding among the higher invertebrates for their extensive regenerative powers, and from the evidence available in 1927 (Korschelt, 1927, pp. 600-1) it seemed probable that in this group regeneration does not depend on the nerve supply. Subsequent publications have not materially affected this conclusion. In the present experiments evidence on the question is . sought from the regeneration of a pair of thoracic limbs in Asellus aquaticus (L.).