226 GEOFFREY SMITH. 



interpi'eted as a return to a juvenile uiidi rt'eren- 

 tiated condition. 



In Part 2 of these studies it has already been pointed out 

 that this interpretation is ruled out by the facts, and this was 

 also pointed out in my earlier work, but not in so detailed 

 and categorical a form, with the unfoi-tunate result that 

 Professor T. H. Morgan, in a recent paper on " Sex iDetermina- 

 tion^' (' Journal Exper. Zoology,' vol. vii, 1909, pp. 343, 344), 

 has adopted this very explanation of my observations. Thus 

 he writes : "The broad abdomen of the castrated male might 

 be considered to correspond to the juvenile state. The only 

 external structure cited by Smith that might seem to indicate 

 that the characters of the castrated males ai-e female rather 

 that juvenile ones is the presence of hairs on the abdominal 

 appendages of Inachus, absent in the young crab, but present 

 in the adult female. Such evidence would not in itself be 

 conclusive, since the presence of hairs may be due to increase 

 in size or to a later moult rather than to latent female 

 characters. Smith concludes that the male sex, and pro- 

 bably the male sex alone, can be so radically modified in its 

 sexual nature as to assume a perfect external hermaphroditism. 

 If, on the contrary, we assume thnt we have here, not herma- 

 phroditism, but an imperfect development of male characters 

 combined with the juvenile condition, we might offer a 

 plausible explanation of the facts." 



I am sorry that any want of explicitness on my part should 

 have misled Professor Morgan, but I cannot accept the state- 

 ment that the only characteristically adult female character, 

 cited by me as being assumed by the infected males, is the 

 presence of hairs on the abdominal appendages. I pointed 

 out in my earlier work ('Naples Monograph,' xxix, pp. 67, 

 70 and 71) that in the young stages of the female, before the 

 adult breeding form is assumed, the abdomen is a com- 

 paratively small flat plate, whereas in the adult it becomes 

 suddenly widened and also takes ou a hollowed trough-like 

 shape, so that the two forms of abdomen are absolutely 

 distinct morphological structures, distinguishable from one 



