Ml'. II. J. Carter on the Spermatuloyy of a new species of Nais. 95 



We have yet, however, to account for the presence of this 

 colouring matter in the sperm-cells of the testes {^^. 6 e), which 

 cells, as before stated, appear to be derived from the dermal 

 cells of the reproductive band, — a point that should certainly not 

 be considered as a natural consequence from their ajjparent 

 identity with the floating-cells only; but it so happeiis that 

 there is a maculated Nais which dwells in the salt- as well as the 

 fresh-water pools here, and which latterly I have also found in 

 the sediment of the jar of Cham before mentioned, where the 

 dermal cells throughout bear amber-coloured globules (the ma- 

 cula:), corresponding in appearance to bile, and answering to the 

 common chemical tests for oily matter, that is to say, dissolving 

 under the influence of jether or a solution of caustic potash 

 respectively. Thus we have the dermal cells in this species, at 

 all events, secreting an oily matter like bile, if not identical with 

 it : and the cells of the reproductive band being but dermal 

 cells apparently modified by hypertrophy, and thus brought into 

 a state similar to the floating-cells of the peritoneal cavity, which 

 appear both to secrete the bile and form the spermatozoa, as the 

 occasion may demand, we have this sort of explanation (should 

 these cells of the testes be hereafter proved to come from the 

 reproductive band) to account for their presenting the charac- 

 teristic brown matter of the sperm-cell of the onsac. 



Thus I have stated all that has occurred to me in the deve- 

 lopment of the spermatozoa in the ovisac of Nais fusca, worthy 

 of mention ; and although I have not been able to follow the 

 developmental process of the spermatozoa in the so-called testes 

 of this worm throughout, yet the laciincp have been supplied 

 from the progressive development of the sperm-cells in the testes 

 of A^ albida, which, proving to be the same as that of the ovisac 

 of N. fusca, thus completes the process for us in the testes of 

 both. Still, where the sperm -cells of the testes in these two spe- 

 cies o^ Nais come from in the first instance, remains undiscovered. 



Let us now, before going to the development of the embryo, 

 compare with one another the changes which take ])lace in the 

 development of the ovum and sperm-cell, in order that we may 

 see how far they correspond. 



Ovum. Sperm- eel I. 



Composition. 



Cell-wall. Cell-wall. 



Endoplasm (primordial film or Endo])lasm (j)rimordial film or 



cell). cell). 



Yelk (composed of fine gra- Albuminous sphere (eonij)<)s(d 



nulcs). of crypto-granular refractive 



matter). 



