232 GKOFFIfKY SMITH. 



a portion of degenerate ovui-y of an infected female, in wliicli 

 islets of ovarian tissue containing; disintegrating ova are seen 

 encapsuled in the connective-tissue slieatli. Fig. 13 is a high 

 power drawing of a small portion of the ovary showing the 

 clear distinction between the germinal nuclei (N), the nuclei 

 of the connective-tissue sheath {rs) and the degenerating ova. 



In a very great number of infected crabs dissected no trace 

 could be found of the remains of a gonad; and in these, allowing 

 for. a certain number in which I overlooked ihe degenerating 

 remains, one must suppose that the process of encapsula- 

 tion by connective tissue and auto-digestion had led to com- 

 plete disappearance. I am unable to state for certain whether 

 the connective-tissue sheath plays an active pait in the 

 absorption of the germinal tissue ; the chief part is clearly 

 due to a simple disintegration of the same nature as is now 

 known to occur in the destruction and absorption of the 

 larval organs of insects during metamorphosis. In this latter 

 process it was formerly held that phagocytosis played the 

 principal part, but it is now known that a process of auto- 

 digestion by fluids is at least as active an agent. 



To conclude this part, I will attempt to outline, in a more 

 satisfactory manner than was possible before, an explanation 

 of why it is that the presence of a parasite should bi-ing 

 about such profound physiological and morphological changes 

 in its host. 



We must clearly define, in the fir^t place, what these 

 changes essentially consist in. It has been shown in my 

 earlier papers, and I trust still more fully brought out in this 

 paper, that the effect of Sacculinaon Inachus is to cause the 

 infected individuals of both sexes to assume adult female 

 characteiistics. This results not only in transforming the 

 males into hermaphrodites with preponderating female char- 

 acters, but also in hastening on the assumption of adult 

 female characters by immature females. The problem, there- 

 fore, resolves itself into this. Why should the presence of 

 •Sacculina cause the host of either sexto becomeadult female 

 in nature '^ 



