SUTTON : SPERMATOGOXIAL DIVISIONS IN BRAC'HYSTOLA MAGNA. 14.") 



When the cells reach this stage they seem to have a tendency t(j 

 roll upon one another, so that the ends of the chromosomes of the 

 one no longer point toward those of the other (figs. 29 and 31), and 

 the spindle, instead of holding its place in the center of the partition 

 wall, comes to lie at one side. ( Fig. J, .v.) 



Almost immediately after the chromosomes reach the centrosome 

 they begin to change, finally losing their homogeneous api^earance and 

 becoming rough in contour, while around each is formed a distinct 

 membrane in place of a common nuclear membrane enclosing all. In 

 each chromosome, the separation of the chromomeres, for such is the na- 

 ture of the change, sometimes results in a hollow space in the middle 

 Avhich makes it appear under the microscoi^e as though longitudinally 

 split. ( Figs. 30 and 34. ) In all but one, this hollowing process proceeds 

 but a short time until it is followed by a general diffusion of the chio- 

 matin within the compartments, which have now become intercom- 

 municating by a resorption of the contiguous portions of their walls 

 at the polar end of the cell, giving the glove-shaped nucleus already 

 mentioned. (Figs. 30 and 31.) One of the chromosomes, which can 

 occasionally be distinguished from the others in the metaphase or 

 anaphases by its rougher contour and greater length (fig. 24), does 

 not join its cavity with that of the others, but remains separate, and 

 further makes itself conspicuous by depositing its chromatin upon 

 its vesicular membrane. ( Figs. 31, 33, 34, and 35.) This is the acces- 

 sory chromosome, and in this condition might be spoken of as the 

 vesicular chromosome. Except after the last spermatogonia! division, 

 this element remains shut up in its vesicle until the following meta- 

 phase, whereas the fusion of the other vesicles may, in rare cases, pro- 

 ceed so far as to reduce the '"fingers'" of the "glove" to a set of 

 shallow pockets in the surface of the nuclear membrane. (Fig. )54.) 



The chromatin of the vesicular chromosome, after remaining for 



some time at the periphery, again recedes, and accumulates at the 



center of the vesicle in a form like that shown in fig. 36, which was 



drawn from a similar stage in the last division. Fig. 13 represents a 



I cross-section of the "fingers'' of the nucleus at this time, the dense 



body at the right being the accessory chromosome. This is the end 



of the telophases, and here the cell enters upon the prophases of a 



inew generation. The chromatin in the common nuclear membrane 



begins to take on the form of a number of fine spiremes, while the 



iiccessory chromosome assumes the irregular shape shown in fig. 15, a. 



\ The spiremes of the nuclear space become shorter and thicker, 



which process is accomioanied by a greater or hjss resorption of the 



partitions between the fingers or pockets of the nucleus ( figs. 15 and 



19), and the accessory chromosome grows gradually smoother and 



