238 NEIL S. DUNGAY. 



the observations on the living material indicate, in the experi- 

 mental cultures different eggs start to develop at different times. 

 This seems, at least in part, to be due to the relatively low activity 

 of the injured sperm cells and to the consequent delay in attach- 

 ment. Likewise it has been hard to get any satisfactory estima- 

 tion of percentages of the various stages present in any preserva- 

 tion. The reason for this lies in the fact that in most cases where 

 marked results w r ere obtained, only a small fraction of the eggs 

 were fertilized and too few fertilized eggs were secured from any 

 one series to get counts large enough to be significant in such 

 complex conditions. The losses in sectioning and staining also 

 add to the difficulties. Yet it has been possible to secure the 

 main facts by going over a large number of slides and by com- 

 paring the results of different experiments. 



Cytological study of the preserved samples from the experi- 

 mental cultures of Nereis eggs shows the following classes of 

 eggs. 



(a) Eggs not entered by sperm. No segmentation. 



1. Polar bodies formed. Jelly not extruded. 



2. Polar bodies formed. Jelly extruded. 



(b) Eggs entered by sperm. Segmentation. 



1. First cleavage not completed. 



2. Multipolar mitosis. Maturation incomplete. 



3. Multipolar mitosis. Maturation completed. Poly- 



spermy. 



4. Miscellaneous abnormal eggs. 



5. Apparently normal eggs many of which would doubtless 



have proved to be defective had they been allowed 

 to develop. 



Cytological study reveals nothing as to the cause of the ab- 

 normalities occurring after the time of the first cleavage, with 

 the single exception of the above mentioned multipolar mitosis. 



(a i) As is indicated by the records made from examination of 

 the living material, by the India ink method, a partial or total 

 lack of jelly formation is one of the striking things which is to 

 be found in nearly all of the experiments. I have never seen 

 this in normally fertilized eggs, either whole or in sections, 



