306 ANIMAL PARASITES. 



corpuscle resembles a little bell, from which the clapper peeps 

 out below. On the seminal corpuscles which have not reached 

 an egg,, the cell-membrane which partially covers the corpuscle is 

 still well preserved, whilst the fatty metamorphosis goes for- 

 ward in the other parts. In the seminal corpuscle penetrating 

 into the egg, the cell-membrane does not appear to penetrate 

 with it, but to remain upon the egg as an empty mem- 

 brane. What becomes of the nucleolar corpuscle is un- 

 known. The finely granular, flocculent mass, at the lower 

 extremity of the seminal corpuscle, does not pass through the 

 fatty metamorphosis, in which, however, the most important, and 

 essentially fertilizing part of the seminal corpuscle participates. 

 In this process the seminal corpuscles sometimes form elongated 

 and narrow, and sometimes short, thick, and bacillar, strongly 

 refractive corpuscles, both in the egg and the albuminigene, 

 and at last become rounded off into oil-drops soluble in 

 ether. 



In animals in which the micropyle is very small and narrow, 

 the seminal corpuscles have a filiform shape in a state of maturity; 

 this they sometimes acquire even within the testis, in which case 

 the penis, like that of the Trematoda, forms a closed, hollow 

 canal, but sometimes only after reaching the female sexual organs, 

 when the penis is imperforate. Circumstances similar to the 

 latter occur in the Mermides, which are nearly allied to the 

 Nematodia. Here the seminal corpuscles have the appearance of 

 a thin bent rod, which remains fast with one end in the develop- 

 ment-cell, and forms a sort of thick head upon the rod. If it 

 loses this head, or if the latter remains seated outside the micro- 

 pyle, the true seminal corpuscle can certainly reach the yelk 

 through the micropyle. Whether similar processes take place 

 in the human Nematodia is a question. The first kind of seminal 

 corpuscle and the larger micropyle, are the usual forms amongst 

 them, if not the only arrangements that occur. 



When the egg is fecundated in the albuminigene by the 

 entrance of the seminal corpuscle, and has gradually acquired a 

 more distinctly ovoid form, it surrounds itself with the contents 

 of the villi of the albuminigene, which solidify upon the vitelline 

 membrane in constantly increasing layers. These tough, albu- 

 minous contents, which are set free by the bursting of the villi, 

 do not mix immediately with water, and at first form clear 

 reddish drops ; afterwards they dissolve in water, and frequently 



