00 Mr. H. J. Carter on the Spermatoluyy of n new species of Nais. 



the hinder part of the cardinal edge of the valves {fig. 3) ; it is 

 deeply notched in the middle of the front edge over the sepa- 

 ration of the valves, and more or less sinuous on the middle of 

 the side edges over the convexity of the valves, as it is figured 

 by Sowerby (' Genera/ f. 2 & 4) * ; but it is often of a much larger 

 size compared with the size of the valves, and more siuuated in 

 front and on the sides than it is here represented. In most 

 specimens of these fossils the dorsal valve is wanting, and there 

 is only a slight fracture between the front of the hinge-margin 

 of the valves, showing the remains of the cast of the shell by 

 which it was attached (fig. 1), as it is represented in fig. 3 of 

 Sowerby's ' Genera.^ 



[A Postscript to tliis paper will be fuunil on page 162. — Ed.] 



IX. — On the ^perinatology of a new species (v/Nais. 

 By H. J. Carter, Esq., H.C.S. Bombay. 



[Concluded from i)age 33.] 



Development of Spermatozoa in the Ovisac. 



1\ the ovisac, pari passu with the ovum, the spermatozoa also 

 frequently become developed ; and this takes place in the follow- 

 ing way : viz. a number of ceils identical to all appearance with 

 the floating-cells of the peritoneal cavity, that is, consisting of a 

 cell-wall enclosing a number of refractive vesicles supported on 

 an albuminous sphere or centre, fill that part of the ovisac which 

 is not occupied by the group of ova. These, at a very early stage, 

 when only a few are present (PI. II. fig. 3 h), may be seen loose 

 and under a spherical or diffluent form (i), or in agglomerated 

 masses of twos, threes or more (A), or attached to the surface of 

 the ovisac, and caudate (/), thus evincing the same plasticity of 

 cell-wall that we have observed in the cell-wall of the floating- 

 cells when adhering together or to the parietes of the perito- 

 neal cavity, while most of the cells present, respectively, a few 

 granules of that light brown matter in their interior, to which I 

 have already alluded as a distinguishing mark of the s])erm-cell 

 throughout. (For more magnified views of these figures, see 

 PI. III. fig. 13 a—f). 



After a time the vesicles enlarge, through nourishment pro- 

 bably derived from the "branchial'^ vessels, and surround, 

 either entirely, or ])artially in groups, globular masses of fine 

 granular matter, which vary in size from that of the sperm-ceil 

 upwards (figs. 14, 15), most of which contain more or less of the 



* In the explanation of the plate, this figure is erroneously said to re- 

 present the forni of the aj)erture of the shell. 



