507 



handle-like portion which projects beyond the level of the other chromo- 

 somes as seen to the left in Fig, 9. More frequently, however, because 

 of its early departure for one pole, it is to be seen a little above or 

 a little below the general level of the equatorial plate as in Figs. 11 

 and 12. Fig. 10 shows it to have passed undivided to one pole. 



The result of the division of the primary spermatocyte is, as 

 regards chromatin content, the production of two dissimilar daughter 

 cells, one of which receives nine, the other eight chromosomes. Since 

 both primary and secondary spermatocytes may frequently be found 

 dividing in the same field and inasmuch as no well-marked intervening 

 resting stages were observed, one is led to conclude that ordinarily 

 the chromosomes rearrange themselves for the second division without 

 passing through the so-called resting period. This is particularly true 

 of material preserved in the spring which is the normal breeding 

 season of the guinea and during which time the development of the 

 sperm goes on at a greatly accelerated pace. 



While at the conclusion of the divisions of the primary sperma- 

 tocytes eight and nine chromosomes respectively were handed on to 

 the respective daughter cells, curiously enough, when the latter as 

 secondary spermatocytes become ready for division, a second reduction 

 in numbers has occurred with the result that half the secondary 

 spermatocytes show five and half, four chromosomes. 



In Fig. 16 is shown a secondary spermatocyte in prophase of 

 mitosis. The comma-shaped odd chromosome is plainly visible. Figs. 13, 

 14 and 15 also show secondary spermatocytes with five chromosomes 

 in late prophase or equatorial plate stage. In the division of this 

 type of secondary spermatocyte the odd chromosome almost invariably 

 lingers and divides late as shown in Figs. 17 and 18. Figs. 20 and 21 

 represent anaphases of dividing secondary spermatocytes which contain 

 five chromosomes, although perhaps a more characteristic arrangement 

 of the late anaphase is represented in Fig. 22 or Fig. 31 where four 

 of the chromosomes mass together and stand somewhat apart from 

 the fifth which is the lately arrived odd chromosome. Fig. 19 re- 

 presents a late metaphase or early anaphase of a five-chromosomed 

 spermatocyte as seen in a smear preparation. 



In this type of spermatocyte which contains five chromosomes it 

 will be observed that apart from the odd chromosome the other four 

 chromosomes are fairly constant in their appearance and comprise two 

 larger and two smaller ones. As a matter of fact, although camera 

 lucida drawings cannot show it because of the restriction of the focus 

 to a very shallow plane, one of the large ones is frequently noticeably 



