Mr. II . J. Carter on the Spermatology of a new species o/Nais. 9 1 



characteristic brown matter. It has already been stated that 

 the vesicles are disposed (according to their number) partially in 

 a group or entirely around the albuminous centre of the float- 

 ing-cell of the peritoneal cavity ; and it is well to bear this in 

 mind, for we shall see presently that when the spermatozoa 

 which are produced from them are half-developed, they hang 

 generally or partially in groups from the globular agglomera- 

 tions, and that this grouping may be thus accounted for (figs. 

 17, 18, &c). At this period (fig. 9) the vesicles are filled with 

 a homogeneous refractive substance, which, upon contraction, 

 after having been some time exposed to the action of the water, 

 shows that it is composed of a granular endoplasm, supporting 

 in one part of its periphery a nucleus, — in fact, that each vesicle 

 is a complete cell (fig. 26 a, b) ; while the material of which the 

 granular mass is composed at this time is so fine, that it has 

 hardly passed beyond the homogeneity of the original albumi- 

 nous mass (fig. 26). 



The next stage in the development of the spermatozoa is that 

 the vesicles become elongated and conical, and that the pointed 

 extremity is applied to the granular mass, whose granular matter 

 is also now becoming progressively coarser (figs. 10 & 16). 



During the fourth stage, the conical point becomes lengthened 

 into a pedicel, which thus presents the first appearance of the 

 spermatozoon, and the material of the granular mass has become 

 still coarser (figs. 11 & 17). 



During the fifth stage (figs. 12 & 19), the spermatozoon grows 

 out to its full length, and disunites itself from the granular 

 mass (fig. 12 e) } which, although keeping together in the ovisac 

 while the spermatozoa are coiled round it, no longer coheres 

 as before when forced out into the water, but, being effete, 

 becomes lost or dispersed as soon as this takes place. 



The part by which the spermatozoon adheres to the granular 

 mass, though not distinguishable here from its linear form, is 

 seen to be the head in Nais albida (figs. 32 & 33) : hence it is 

 the head which would appear to be developed first; and so 

 Kolliker has stated, but not however in the way thus indicated, 

 for he has observed that the whole of the spermatozoon becomes 

 developed first in a cell within the vesicle (fig. 21 a), from which 

 it gets into the cavity of the latter, and then forces its head out 

 of one part to become attached to the granular mass*; but in 

 all instances where the half-developed spermatozoa of this Nais 

 have had the contents of the vesicle at their extremities con- 

 tracted from long exposure to the water or from the addition of 

 iodine, they have presented a granular aspect. This, however, 

 may be, and probably is, owing to the extremely fluid state of 

 * Art. " Semen," Cyclop, of Anat. and Physiology, p. 486. 



