286 DR. J. B. GATENBY ON THE GERM-CELLS AND 



One small point I may mention with regard to any possibility of self- 

 fertilization in Grantia : the sole individual in which I found unripe 

 spermatids also contained oocytes just being fertilized, showing that the 

 sperms must have come from some other sponge, or otherwise one would 

 have found later stages in spermatogenesis. 



As a matter of fact, the whole question of sex in sponges is far from being 

 definitely settled, for I doubt whether certain previous observers of marine 

 sponges have really identified the true sperm-stages. 



(f) Spermatogenesis in Grantia. 



Haeckel in his ' Kalkschwamme ' figures small " sperm-balls " just under 

 the gastral epithelium, much in the same position as in Dendy's figures. 

 Neither Haeckel nor Dendy have produced convincing evidence as to their 

 " sperm-balls." 



Subsequently to my writing the account of Grantia spermatogenesis given 

 on page 272, I had the opportunity, through Professor Dendy's kindness, 

 of seeing not only his own " sperm " stages, but also those of Dr. Polejaeff. 

 In figs. S6-93 of Professor Dendy's plate. 26 are drawn what this observer 

 describes ;is " sperm-morulse/' with spermatozoon heads; he has also 

 described the derivation of these morulse from other cells which he believed 

 to be spermatogonia and spermatocytes. On pi. 26. fig. 94 he gives figures 

 from Dr. Polejaeff's slides. After carefully reading Dendy's account, and 

 having seen his preparations, I have little hesitation in claiming that what 

 he has described are certainly not sperm-stages of any sort; I believe that 

 these bodies he describes are parasites or inquilines of some kind, probably 

 of plant nature. Dr. Polejaeff's sperm-balls are, I consider, nothing more 

 than some protozoan, while the granules inside the cell are not individual 

 cells, but discrete cytoplasmic aggregations. Moreover, neither Dendy nor 

 Polejaeff figure tails on their spermatozoa, while I find tails on my 

 spermatids*. 



I believe that there is no doubt that the cells I have described are true 

 stages of spermatogenesis, and I sectioned twenty-five sponges before I 

 found them. I wish to emphasize this fact, for other observers have found 

 the same scarcity of spermatogenesis stages in sponges, and this is one 

 reason why two observers (and probably three) identified either parasites or 

 inquilines as sperm-stages. 



Wilhelm Gorich in Spongilla Jiuviatilis describes what are undoubtedly 

 stages in spermatogenesis ; his description of the formation of the spermato- 

 zoon from the spermatid is quite detailed, but he mentions neither mitochondria 

 nor Golgi apparatus. In Spongilla the sperm-stages lie inside a wall of 

 nurse-cells ("Cystenzellen"'), somewhat as in Grantia. In Sycandra raphanus 



* At the meeting- of the Society, after I had read this paper, Prof. Dendy, in reply, 

 abandoned his previous views with regard to his " sperm-niomla?," and stated that in two 

 other sponges he had found stages like those which I have described in this paper. 



