244 BULLETIN OF THE 



it always arises from that part of the yolk where the constriction sub- 

 sequently appears. The statement that " Grosse sowie Anzahl ist sehr 

 differirend," can only have been the result of a superficial study of these 

 bodies. 



P. S. — Two papers on early stages in the embryology of Limax and 

 Helix respectively, one by Mayzel and th^ other by Perez, will be con- 

 sidered in an Appendix. 



II. Review of Maturation, Fecundation, and Cell-Division. 



1. Cell-Division. 



The significance of the now well-established cell theory is hardly 

 more far-reaching than is that of its legitimate offspring : the discovery, 

 on the one hand, of the substantial identity of cell-division, whether in 

 the animal or the vegetable kingdom, whether at the beginning or at the 

 close of that cycle of events which makes up what we call the life of the 

 individual ; and, on the other hand, the growing conviction that fecunda- 

 tion is the reunion of forces which have suffered a complementary differ- 

 entiation in cells whose corresponding parts become directly commingled 

 in this act. 



As the influence of the cell theory on investigations for the past forty 

 years can hardly be overestimated, so we may confidently look forward 

 for no mean outcome from the impetus imparted to biological research 

 by these more recent achievements. The influence of studies on cell 

 phenomena culminating in such broad generalizations, if less signifi- 

 cant to the popular mind than evidences of a process of evolution drawn 

 from the structure and habits of adult beings, is none the less securely 

 intrenching the belief in the consanguinity of all living things. 



Of all the phenomena connected with cell-division, that which may be 

 designated as the metamorphosis of the nucleus has recently received 

 most attention. It is that which has remained almost up to the present 

 time superficially observed, not at all understood, and therefore the 

 cause of many conflicting statements. Some portions even of the more 

 obscure changes which take place within the cell during the nuclear 

 metamorphosis were long ago seen, though hardly comprehended. 

 These observations were for the most part limited to the changed ap- 

 pearance of the protoplasm surrounding the nucleus, — the stellate 

 figures, — and were made on one or the other of the two cellular ele- 

 ments of sexual reproduction. Previous, then, to the consideration 

 of the metamorphosis of the nucleus, the observations on the stellate 



