DIFFERENCES IN VIABILITY IN REGENERATES. 



Here, however, it is impossible to give full proof of this until 

 further material can be examined. But it is at least suggestive 

 that Dr. Gatenby himself 1 has found in the normal fertilization 

 of a closely-related sponge that the spermatozoa do not pene- 

 trate the oocytes directly, but enter collar-cells. Within these 

 they undergo a partial transformation to vesicular nuclei (at this 

 stage closely resembling the bodies found in the cells of the re- 

 generating masses), and are then transferred, by the migration 

 of the collar-cells, to the oocytes, into whose substance they pass. 

 Within the maturing ova they undergo the remainder of the trans- 

 formation to male pronuclei, and then effect fertilization in the 

 usual way. If the bodies within the cells of the regenerating 

 masses do prove to be what they appear to be, namely, half- 

 transformed sperm-heads, two interesting points emerge. The 

 first is that somatic cells can exert an attraction on spermatozoa 

 comparable to that exerted by oocytes. In normal fertilization, 

 only collar-cells within a certain radius are entered by sperma- 

 tozoa ; thus it might be supposed that the attraction was exerted 

 by the oocyte through the collar-cells, and that these had no at- 

 traction of their own. That this is not so, would be proved if 

 our interpretation of the bodies in the regenerating masses is 

 correct. But we would have to suppose that this attraction of 

 the collar-cells was much less than that of the oocytes, whose 

 presence thus would prevent collar-cells beyond a certain dis- 

 tance from oocytes from being entered. 







In the second place, the definite but slight attraction of the 

 collar-cells for spermatozoa would be correlated with the definite 

 but partial transformation of the sperm-head to a nucleus within 

 them. This correlation between degree of attraction and degree 

 of nuclear transformation is what would be expected on such a 

 theory of fertilization as Lillie's. 



It is to be hoped that any worker having the opportunity to ex- 

 amine ripe sponge spermatozoa will undertake an investigation of 

 the problem raised in this note. 



In conclusion I have to thank Dr. Gatenby for his interest and 

 for permission to publish the results discovered by him. 



1 " The Cytoplasmic Inclusions of the Germ-Cells. Part VIII. Fertilization 

 and Gametogenesis in Grantia compressa," Journ. Linnaean Soc., 1920. 

 May 28, 1920. 



