348 ABSTRACTS OF PAPERS. [VOL. II. 



show but half the usual number of chromosomes, namely, 

 eighteen instead of thirty-six. The same conclusion is reached 

 by the study of the other internal phenomena, which differ in 

 a characteristic way from those occurring in normal fertiliza- 

 tion, though showing an interesting parallel to them. 



The eggs, even of the same individual, show a very high 

 degree of variability in their response to the solution. Great 

 numbers of incomplete or abnormal forms of mitosis occur. 

 The most interesting of these are cases in which the nucleus 

 becomes the center of formation of a single aster (monaster), 

 which never resolves itself into an amphiaster but nevertheless 

 passes through periodic changes parallel to those occurring in 

 complete mitosis. Thus, such an aster may appear, nearly dis- 

 appear, and reappear as many as six times in succession, the 

 nucleus simultaneously disappearing and re-forming. In such 

 cases the chromosomes divide, probably at each disappearance 

 of the nucleus, and may thus become very numerous, without 

 division of the nucleus or of the cell body. In other forms of 

 incomplete mitosis the single aster may give rise to an amphi- 

 aster, but the nucleus fails to divide. 



In all the eggs capable of development, the initial change is 

 an irregularity in the cytoplasmic meshwork, followed by the 

 appearance of a primary radiation centering in the nucleus, 

 the gradual formation of a perinuclear clear zone of hyalo- 

 plasm, and the growth of the nucleus. In many of the eggs a 

 number of separate asters (cytasters, equivalent to the " arti- 

 ficial astrospheres " of Morgan), having no direct relation to 

 the nucleus, are formed in the cytoplasm in addition to the 

 primary radiation. At the centers of these asters hyaloplasm 

 likewise accumulates. Growth of the nucleus is followed by 

 disappearance of the nuclear membrane, the rays of both the 

 primary radiation and of the cytasters meanwhile becoming 

 much reduced and in some cases nearly disappearing. After 

 a short pause this is followed by a redevelopment of the rays, 

 and in typical cases the nuclear area (the center of the former 

 primary radiation) has now formed two centers of radiation, 

 producing a typical amphiaster. When no cytasters are present 

 (a relatively rare case) cleavage may proceed nearly as in 



