Sexual Products in Spongilla. 439 



of the mature ovum is smaller and poorer in chromatin than 

 that of the immature ovum. Even in the former, however, 

 it never becomes " a perfectly homogeneous vesicle " (Goette) ; 

 it always contains a distinct nucleolus, in a nuclear space 

 Avhich is certainly large and clear. 



Similar nuclei may be detected by means of double-stain- 

 ing in all segmentation-spheres. Even in rather thick 

 sections of the younger stages they shine out red from the 

 blue vitelline masses. In older stages they are the more" 

 easily visible, because they are surrounded only by a single 

 layer of vitelline globules. Finally, not only the number 

 but also the size of the vitelline elements diminishes still 

 more by disintegration. But I must decidedly deny any new 

 formation of nuclei by direct transformation of vitelline 

 globules. The cell-nuclei of the young Spongilla are rather 

 derived in uninterrupted sequence from the nucleus of the 

 fecundated ovum, and here also, as Ganin indeed conjectured, 

 the principle applies : — "' Omnis nucleus e nucleo." 



Although, in the course of the process of segmentation, I 

 was unable to observe any karyokinetic figures (no doubt in 

 consequence of the quantity of vitellus in the ova), they 

 forced themselves upon me in the greatest abundance and 

 multiplicity during the spermatogenesis. The extraordinary 

 minuteness of the object certainly added considerably to the 

 difficulty of the investigation ; nevertheless, besides the com- 

 monest coil-form, representatives of the star-, spindle-, and. 

 barrel -forms could be recognized. Without going further into 

 details, I may remark that the sperm-formation takes place 

 in accordance with the second type established by Polejaeflf* 

 for the sponges. I can therefore confirm the short statement 

 made by F. E. Schulze f in his classical " Investigations upon 

 the Structure and Development of the Sponges," according to 

 which Spongilla approaches Halisarca as regards these pecu- 

 liarities. There is therefore no formation of a special covering- 

 cell or of a primordial seminal cell. On the contrary, a cell 

 distinguished by its particularly large, strongly colourable 

 nucleus, being converted into the sperm-mother-cell, divides 

 repeatedly and, indeed, always with formation of filaments, 

 while surrounding parenchyma-cells close together to form a 

 follicle, as in the case of the ovum. The follicle is, how- 



* N. Polejaeff, "Ueber das Sperma und die Spermatogenese bei 

 Sycandra raphmius,^^ in Sitzb. der Akad. Wiss. in Wien, Bd. Ixxxvi. 

 p. 276 (1882). 



t F. E. Schulze, " Untersuchungen iiber den Bau und die Entwicklung 

 der Spongien, II. Die Gattung Halisarca,^' in Zeitschr. fiir wiss. Zool. 

 Bd. xxxviii. (1877). 



