No. I.] THE EGG OF UMAX AGRESTIS. 219 



single Qg^. Most of the sperm-nuclei had become vesicular 

 and had migrated toward the egg-nucleus at the upper pole. 

 These eggs were very irregular in outline, and the cytoplasm 

 showed that degeneration had already begun. None of these 

 polyspermic eggs showed any evidence of division, and in none 

 of tlicni was there any evidence of the presence of centrosomes or 

 asters. I have occasionally found isolated cases of polyspermy 

 among normal sets of eggs, but except for the presence of 

 more than two nuclei, they gave no evidence of being abnormal. 

 Polyspermic eggs are evidently incapable of development in 

 Limax agrestis ; normal development ceasing before the sperm- 

 nuclei attain their full growth and, therefore, before the asters 

 appear. 



2. Abnormalities Other than Polyspermy. 



A few abnormal eggs showed very peculiar bodies in connec- 

 tion with the sperm-nucleus. I have seen a number of eggs at 

 the stage when the asters usually appear, in which the sperm- 

 nucleus is accompanied by two relatively large spherical bodies, 

 which lie out in the cytoplasm on each side of the sperm-nucleus. 

 These bodies are on the side of the sperm-nucleus away from 

 the egg-nucleus, but from their number and evident connection 

 with the sperm-nucleus one can scarcely avoid the conjecture 

 that they bear some relation to the centrosomes. I have been 

 much puzzled by these bodies and thought that I might be 

 dealing with two species of Limax, in one of which the centro- 

 somes appeared as naked sphaeres. I am indebted to Prof. 

 H. A. Pilsbry, of the Philadelphia Academy of Natural Sci- 

 ences, for having identified all the individuals as belonging to 

 the single species, Limax agrestis (Linne). 



In two instances at least, the eggs in which these structures 

 occur are known to have been abnormal, for the apposition of 

 the egg and sperm-nuclei did not occur until five hours had 

 elapsed after the eggs were laid. Normally this stage was 

 reached within two hours. 



Before the extrusion of the second polar globule the upper 

 poles of the eggs became very irregular in outline and formed 

 pseudopod-like projections from the upper surface. After the 



