184 M. E. Claparede on the Formation of the Egg 



come at once upon a dispute, the counterpart of that which we 

 have already referred to in connexion with the formation of the 

 ovum. Some assert that the seminal corpuscles are from the 

 first surrounded by a membrane; others will not admit the 

 existence of this membrane. The principal supporters of the 

 latter opinion are Siebold, Nelson, Bischoff, and Thompson. 

 Keichert and Meissner hold the former. Here, again, the truth 

 appears to lie in the middle, or, if it be preferred, on both sides. 



The turning-point of the whole discussion is formed again in 

 this case by Ascaris mystax. Unfortunately, we have had but 

 few cats at our disposal, and in these we only found female Asca- 

 rides. As, however, we have obtained male individuals oi Ascaris 

 suilla, this deficiency is easily got over. The mature seminal 

 corpuscles of the two species are so much alike, that it is per- 

 fectly impossible to distinguish them ; we may therefore well 

 suppose that the course of development will be essentially the 

 same in both cases. 



The blind extremity of the genital tube is full of small colour- 

 less vesicles. There can be no question about Meissner^s male 

 germ-cells. It was as impossible for us as for Nelson, Bischoff, 

 and Thompson to find them, and it is not probable that they 

 could have escaped so many observers. As the colourless vesi- 

 cles progress downwards in the genital tube, they surround 

 themselves with a granular mass, which consists of strongly 

 refractive granules and a colourless connecting substance. The 

 contents of the male genital tube are then perfectly similar to 

 those of the vitellogene, and the more so as the seminal corpus- 

 cles in formation are of a pyriform shape, with their apices 

 directed towards the axis of the organ. The apices adhere more 

 or less to each other, but a true rhachis is not produced by this 

 means. Each corpuscle now appears like an ^^^', the clear 

 vesicle shines through, like a germinal vesicle through the yelk. 

 This deposition of granules was first described by Siebold in 

 Ascaris paucipara. It was, however, controverted, evidently 

 incorrectly, by Reichert; but the latter observed Strongylus 

 auricularis and Ascaris acuminata, in which the seminal elements 

 are comparatively small. In Ascaris paucipara and Ascaris 

 suilla, on the other hand, the various stages of development of 

 the seminal elements are considerably larger, so that they per- 

 mit observations to be made with much greater certainty. 



In the lower part of the testis, the corpuscles which were 

 previously pyriform, or rather pyramidal, become rounded ; the 

 nucleus (the clear vesicle) disappears altogether. Each corpuscle 

 then forms a granular sphere. The granules soon pass to one 

 particular side of the globule, so that it then represents a clear, 

 transparent sphere, furnished with an aggregation of granules 



