2l8 J. MCA. KATER. 



frequently that it is not worth while to devote space to them here 

 (Boveri, 1909; Moenkhaus, 1904; Conklin, 1912; Richards, 

 1917). 



The vacuolization of plant chromosomes has not been so fre- 

 quently described and is not so easily studied because the chromo- 

 somes do not take up as much achromatic material as do the 

 chromosomes of animal eggs. The early vacuolization of the 

 chromosomes of Vicia was studied by Sharp (1914). This plant 

 has large chromosomes and affords very favorable material for 

 the botanical approach to the subject. The chromosomes of 

 Phaseolus are small and not suited to a study of this kind. Their 

 great value for the present work lies in the fact that when the 

 chromosomes come in contact with each other at the poles of the 

 spindle they are perfectly parallel with each other. This fact, 

 together with their rounded ends makes it possible to identify 

 the linin strands as the linin sheaths of chromosomes. 



Similar linin strands have been figured in the resting nuclei of 

 other plants (Martins Mano, 1904; Bergs, 1906; Lutman, 1925). 

 These investigators as well as Derschau (1904) have also described 

 the telophase in a manner which indicates that the condition in 

 those forms on which they were working is very similar to that 

 of Phaseolus. 



Prophase. In the only case in which chromosomal vesicles 

 have been traced through the resting stage of the nucleus 

 (Richards, 1917) the figures are so clear and convincing that one 

 has no cause whatever to doubt the endogenous formation of 

 chromosomes. The new chromosomes are formed in the pro- 

 phase vesicles and are set free by the dissolution of the old walls. 

 After reading this account of the formation of chromosomes in 

 Fundulus it was very surprising to find that they are not formed 

 in the same way in Phaseolus, but that the chromosomal vesicles 

 merely lose their achromatic content, contracting and giving rise 

 to the new chromosomes, the old linin sheath apparently being 

 continuous from one division through the next. 



Wager concluded that the nuclear membrane of Phaseolus 

 dissolves. However, his figures do not entirely justify that con- 

 clusion and indicate that his material was identical with that 

 used in the present study. The author knows of no account at 



