230 GEOFFRKV SMITH. 



this fact, which lias an importiint bearing on the whole 

 meaning' of parasitic castration, will be discussed later, but it 

 has been introduced here as a final nail in the cofHn of the 

 theory which attempts to explain the effects of parasitic 

 castration as due to arrested development or the assumption 

 of juvenile characters. Possibly the use of the term " parasitic 

 castration " has had something to do with perpetuating this 

 unfortunate error, the analogy between ordinary operative 

 castration or mechanical removal of the gonads and their 

 degeneration owing to the presence of a parasite being, as 

 Pi-ofessor Sedgwick has pointed out, extremely small. In 

 parasitic ''castration" the degeneration of the gonad is not 

 bi-ought about by the parasite mechanically removing or 

 attacking the gonad, but by its setting up a deep-seated 

 alteration of the metabolism of the host which secondarily 

 reacts on the gonad. We may now enter into the question 

 of the method of degeneration of the gonad. In the above 

 paragraphs I trust that the following conclusion has been 

 tlioroughly vindicated. The moditication of the male Inachus 

 by the parasite Sacculina consists in the assumption by the 

 male of adult female sexual characters to a greater or less 

 degree of perfection ; in neither sex can the modifica- 

 tion be ascribed to arrest of development or the 

 assumption of a juvenile immature condition. 



As I have shown in my earlier work (loc. cit., pp. 72-74) 

 the degenerate condition of the ovaries and testes with their 

 ducts in infected Inachus is due to two causes : firstly, an 

 arrest of growth, so that the gonad tends to remain in the 

 same condition as it Avas when infection took hold, and 

 secondly, to an actual absorption of the tissues of the gonad 

 and their final disappearance, a process which was often 

 accompanied by an actual irruption of the roots of the 

 parasite into the germinal tissues. The ari-est of growth of 

 the gonad and the first stages of degeneration, at any rate in 

 the male, were shown to be independent of the irruption of 

 the Sacculina roots. 



The method of absorption and disappearance of the gonad 



