96 Mr. H. J. Carter on the Spermntology of a new species of Nais. 



Ovum. Sperm-cell. 



Composition. 



Nucleus (or "germinal vesicle"). Nucleus. 



Nuclei (or points in the endo- Vesicles (or cellules round the 



plasm of the "germinal ve- albuminous sphere). 



sicle'^. 



Changes. \st stage. 



Cell-wall continues. Cell-wall continues. 



Endoplasm disappears. Endoplasm disappears. 



Yelk-granules become large Albuminous sphere becomes 



and multiplied. perceptibly granular. 



Nucleolus (or "germinal spot'^) Nucleus perishes. 



perishes. 



Nuclei, or points in the endo- Vesicles develope spermatozoa 



plasm of the " germinal ve- which attach themselves to 



side," become surrounded the albuminous sphere. 



by cells respectively. 



2nd stage. 



Nucleus or "germinal vesicle" Spermatozoa fully formed and 



disappears (that is, bursts, separated from the albumi- 



and the " nuclei," now sur- nous spheres or granular 



rounded by cells, are dis- masses, 

 persed in the yelk ?)*. 



Yelk persistent. Granular masses effete. 



Zrd stage. 



Ovum receives the spermatozoa. Speriiuitozoa enter the ovum. 



Velk-granules are resolved into 

 a crypto-granular mass. 



Yelk, having received its final 

 envelopes and been laid, un- 

 dergoes deduplicative sub- 

 division. 



Thus we see that the differences between these processes are 

 so great, that they cannot even be considered analogous. The 

 new cells produced by the ovum and si)erm-cell respectively, 

 that is, the cells of the nucleus and the " vesicles," are the only 

 products that we can compare with one another ; and these are 

 so far different, that one is produced in the germinal vesicle, and 

 the other out of it, while the yelk of the ovum no doubt affords 

 nourishment to the germinal vesicle, as does the granular mass 



* I have also observed sonic of these cells (fig. 12 A) to be again charged 

 with nuclei, indicative of their undergoing a further nudtiplieation after 

 having been dispersed in the yelk. 



