Mr. Hi J. Carter on the Spermatology of a new species o/Nais. 93 



brown matter unmistakeably marks the spermatophorous mass 

 throughout, from the sperm-cell to the full development of the 

 spermatozoa. 



Let us now see what evidence we possess of connexion between 

 the single small sperm-cell and the large globular masses sup- 

 porting the vesicles, from which the spermatozoa are developed 

 in the ovisac. In the first place, the only cells which are pre- 

 sent in the ovisac, before the process leading to the development 

 of the spermatozoa commences, are the ova en groupe and the 

 sperm-cells, which at this time are identical with the floating- 

 cells (fig. 9 a, c). It cannot be the ova, then, which develope 

 the spermatozoa ; hence we have only the sperm-cells left. Next 

 we find several of the sperm-cells cohering together through the 

 plasticity of their cell-walls, and forming agglomerations of dif- 

 ferent sizes ; hence the large globular masses are accounted for 

 (figs. 3 k and 13 d) ; while the presence of some cells or masses 

 not exceeding the diameter of the single sperm-cell, yet bearing 

 spermatozoa, shows that cells or masses, from the size of the 

 sperm-cells up to that of the largest agglomerations, may bear 

 spermatozoa (fig. 27). Lastly, having seen that the number of 

 vesicles in the sperm-cells is very variable, and that these en- 

 tirely surround the albuminous centre when numerous (13 a, b), 

 or, when scarce, are situated on one part of it in a group (fig. 5 d), 

 while they may be also partially or entirely absent, we have thus, 

 in the early stage of the single sperm-cell, that which we have 

 afterwards in the agglomerated mass, viz. the vesicles covering 

 the mass entirely, or only attached to one part of it (figs. 17 & 

 18). Besides, it is very common to see the agglomerated masses 

 themselves, at an early period, presenting groups of vesicles 

 here and there upon them, indicative that the cells forming these 

 parts of the masses respectively, alone bear vesicles (fig. 13 d). 

 One point more deserves notice here, and one, too, which has 

 not been well accounted for by the authors of the excellent 

 article to which I have alluded, viz. the disappearance of the cell- 

 wall or mother-cell in the globular masses. But this yields 

 immediately to explanation when we know the cell-wall of the 

 sperm-cells to be plastic, and therefore easy of disappearance in 

 several ways ; indeed, it is so evanescent, that in many of the 

 cells of the reproductive band, as well as of the hepatic layer, 

 where the vesicles have not undergone the least enlargement, 

 the cell-wall is almost as often absent as present. However, one 

 instance has occurred to me where the cell-wall seemed to have 

 remained ; and this was where the spermatozoa, which were more 

 than two-thirds developed, had grown out from single sperm- 

 cells —judging from their size (fig. 27). Here, then, it would 

 appear that the mother-cell had become persistent from harden- 



