THE ACCESSORY CHROMOSOME. 53 



fragments of the original chromatin nucleolus, may still be seen 

 in the nucleus, and often up to the monaster stage. At the time 

 when the chromosomes have attained their definitive form, it 

 usually becomes likewise elongated and dumb-bell-shaped ; in 

 the majority of cases it appears to assume this form before the 

 nuclear membrane disappears. Thus it looks like a diminutive 

 chromosome among larger ones. As the true chromosomes now 

 stain with saffranine it likewise resembles them in coloration. 

 This peculiar structure acted like a nucleolus in the rest stage, 

 but in the monaster is destined to lie in the equator among the 

 chromosomes, where it also becomes divided in metakinesis, 

 and so terminates in acting like a chromosome, as at the com- 

 mencement it has been formed from one. 



34. "In a few cases, so few that they must be considered 

 abnormal, a whole undivided chromosome passes into a second 

 spermatocyte, but I have met with only two or three such cases. 

 Henking found in Pyrrhocoris and later in some other cases, that 

 the second spermatocytes receive an unequal number of chro- 

 mosomes, i. e., that one of them may frequently if not usually 

 receive a whole undivided chromosome ; either Pyrrhocoris shows 

 a marked peculiarity in this respect, or else Henking had mis- 

 taken either a yolk globule or a chromatin nucleolus for an 

 undivided chromosome. . . . Each second spermatocyte appears 

 as a rule, if not always, to receive a half of the original chromatin 

 nucleolus. 



35. " The 7 chromosomes and the chromatin nucleolus grad- 

 ually become arranged in the equator of the spindle, their axis 

 parallel to the latter, and the plane of their constrictions perpen- 

 dicular to it. Then follows the metakinesis, with a consequent 

 transverse (reduction) division of all the chromosomes, and 

 apparently in most cases of the chromatin nucleolus, with the 

 result that each daughter cell (spermatid) receives 7 daughter 

 chromosomes and I daughter nucleolus." 



36. Paulmier ('99) records in his observations that " These in- 

 teresting bodies (the small chromosomes) were first recognized 

 in the equatorial plate of the spermatogone divisions in the form 

 of two chromatin masses very much smaller than the chromo- 

 somes and connected with them by chromatin bands. In the 



