The gonopodium of the poeciliid fishes has been niade the subject of a number of studies in morphogeiiesis and regeneration which were designed to gain insight into the mechanisms which control the transformation of tlie unspecialized anal fin of the juvenile male into a complicated copulatory organ. The studies hare employed observation of normal morphogenesis of the anal fins of males and females, the application of androgenic hormones to normal young males and females, the excision or extraction of rays of tlie fin in females and in young and mature males, and the application of androgenic hormones to males and to females in which regeneration was occurring in the anal fin.
The writer (Turner, '41b) excised or extracted rays and groups of rays of the anal fins of juvenile males, developing males and mature males of Gambusfia afittis to determine the effect upon normal growth and differentiation of the various parts of the fiii of the loss of parts or of alterecl growth rates. Some of the coiiclusions, among others, were :
(1) that regenerating fins of juvenile males were capable of developing normal gonopodia, (2) that gonopodia, developed from fins which were operated upon during metamorphosis 1 This rescarrli has been supliorted hy R grant from the Graduate Rcliool of Northwestern University.