HISTORY OF CHROMOSOMAL VESICLES IN FUNDULTJS. 265 



has progressed farther than in this case. These split chromo- 

 somes are suggestive, however, when compared with such chromo- 

 somes as shown in Fig. 2. 



The manner of attachment of the fiber to the chromosomes and 

 the steps leading to the metaphase plate condition are shown 

 in Figs. 24 and 25. Fig. 24 is an oblique section in which there 

 is only one sphere. The walls of the vesicles at the polar end of 

 the nucleus are gradually disappearing and the fibers are making 

 their way to prophase chromosomes ; traces of the walls however 

 can yet be seen. In the next figure the attachment of the fibers is 

 practically completed and the chromosomes have become defin- 

 itely placed upon the spindle. While in general they were ori- 

 entated in the prophase with their long axis in the spindle axis, 

 they become definitely "drawn" into place with the attachment 

 to the fibers. The condensation of the chromosomes and their 

 final arrangement on the spindle completes the cycle and brings 

 us again to the stage shown in Fig. I. 



These' last two figures are interesting also for their likeness 

 to the conditions found by Van der Stricht in the egg of Thysano- 

 zoon. In this form the spindle and its fibers can be differentiated 

 into several parts. The principle cone, "cone principaux," of 

 fibers corresponds to the mantle fibers and is composed of those 

 which attach to the chromosomes themselves. Just outside 

 these but still in the area of the nucleus is a cone of fibers which 

 do not attach; this Van der Stricht called "cone accessoire." 

 Finally out in the cytoplasm is to be seen a series of the fibers 

 which interlock with those from the other end of the spindle; 

 these are the "fibers cytoplasmique." In Fundulus eggs exactly 

 the same conditions seem to prevail (Figs. 25 and i). 



As the central spindle fibers make their way to the chromo- 

 somes and attach to them there is a gradual movement of the 

 chromosomes to the equator of the spindle to form a plate. 

 During this movement the last stages in the condensation of the 

 chromosomes takes place, resulting in the formation of the 

 densely staining metaphase rods, such as were figured by Moenk- 

 haus and Miss Morris. As they condense the chromosomes 

 increase in thickness, so that the metaphase chromosome is both 

 shorter and broader than that of any other stage. The nuclear 



