92 Mr. H. J. Carter on the Speniiatoloffy of a new species o/Nais. 



the matter composing the spermatozoon at this early period ; 

 for in Nais albida always, and even in N. fusca sometimes, the 

 tails also project from the opposite side of the vesicle at the 

 same time (figs. 25, 31, 32), thus proving that the whole body 

 of the spermatozoon, at least in these cases, is formed at this 

 early period. I have, however, not been able to see this or the 

 daughter-cell in the sperm-vesicles of either of these Naides ; 

 nor have 1, of course, been able to see that the spermatozoon is 

 formed in the nucleus, as also stated by Kollilcer*, — that is, I 

 suppose, in the nucleus of the daughter-cell of the vesiclef, — 

 probably from the smallness or un suitableness of the materials 

 I have had to deal with. 



Among the contents of the ovisac from which the spermatozoa 

 are thus developed, there are some granular masses which are 

 surrounded by vesicles much larger than others (fig. 26), and 

 these vesicles, although filled apparently with homogeneous 

 refractive matter, like the rest, show, by the contraction of this 

 into a globular form after they have been some time exposed to 

 the action of water, that it also consists of a granular mass of 

 endoplasm bearing in one part a nucleus {a,b). How such 

 large vesicles are to bring themselves down to the size of those 

 which only bear one spermatozoon each (fig. 16 a), I have not 

 been able to understand ; and never having observed more than 

 one spermatozoon developed respectively from the vesicles at- 

 tached to the granular masses, and these vesicles all small ones, 

 I am at a loss to conceive what happens to the large vesicles, un- 

 less they become still larger, and then develope several cells in 

 their interior, each of which bears a spermatozoon, as the pre- 

 sence of such cells now and then in the ovisac of N. fusca would 

 seem to indicate (figs. 29, 30). That several spermatozoa may 

 be developed from one vesicle is a common occurrence, and 

 fig. 37 is an instance of it in Ampullaria ; but whether this is 

 another instance of each spermatozoon being developed from a 

 separate cell, or the whole mass of cell-contents has split up 

 into the bundle of spermatozoa thus represented, I am not called 

 upon, or prepared even, here to discuss. Views respecting this 

 will be found in the admirable article on " Semen," to which I 

 have alluded. I must confine myself here to the common and 

 only course of development in Nais fusca that I have been able 

 to follow with certainty ; and that is the one above described, 

 wherein not only a gradual development of the spcrmatophorous 

 vesicles can be traced from their first presence in the sperm- 

 cell to the time when they become conical and present the 

 first appearance of the spermatozoon, but the })rcsence of the 



* Art. " Semen," Cyclop, of Anat. and Physiology, j). 497- 

 t Is this a " nucleus," or the embryo of the spcrnuitozoon? 



