400 EDWIN G. CONKLIN. 



carbonic acid and various other chemical substances (Conklin, 

 1912). These different types of modified mitoses may be classi- 

 fied under the following heads: (i) Scattering of chromosomes 

 and their failure to unite into a single nuclear vesicle, (2) amitotic 

 or mitotic division of the nucleus without division of the cell 

 body and the subsequent division of such binuclear or poly- 

 nuclear cells, (3) separation of chromatin and achromatin and 

 formation of cytasters, (4) persistence of nuclear membrane and 

 formation of chromatic connections between daughter nuclei. 



I. SCATTERING OF CHROMOSOMES AND THEIR FAILURE TO UNITE 

 INTO A SINGLE NUCLEAR VESICLE. 



In the late anaphase of normal mitoses the chromosomes of 

 the daughter plate stick together so that when the individual 

 chromosomes begin to take in achromatic substance and to 

 swell up into chromosomal vesicles the whole plate is converted 

 into a mulberry-like mass which later becomes a single nuclear 

 vesicle either by the fusion of the separate chromosomal vesicles 

 or by their closer approximation. There is a growing body of 

 evidence that in certain cases at least these closely appressed 

 chromosomal vesicles do not completely fuse with one another 

 but preserve their individuality (Bonnevie, 1908, for Ascaris 

 and Allium; Vejdovsky, 1912, for Ascaris and Decticus; Wenrich, 

 1916, for Phrynotettix; Richards, 1917, for Fundulus). In other 

 cases, when it is not possible to recognize a distinct vesicle for 

 each and every chromosome, maternal and paternal chromosomes 

 may form more or less distinct vesicles (Hacker, 1895, for 

 Cyclops; Conklin, 1901, 1902, for Crepidula). 



In certain abnormal conditions, and especially by means of 

 temperatures higher than normal and by hypertonic sea-water, 

 the division and separation of daughter chromosomes may be 

 delayed or stopped and the chromosomes scattered along the 

 length of the spindle (Figs. 9, 10, 29). After the chromosomes 

 have reached the poles of the spindle, they may be separated 

 from one another and remain scattered more or less widely in 

 the cell. If the temperature is not too high (34-35 C.) each 

 separate chromosome will then swell up to form a separate 

 vesicle, or if two or more chromosomes are in close contact they 

 may form a single vesicle of larger size (Figs. 7, 9-12). 



