576 



frcm the other members of the equatorial plate. Fig. 8 repre- 

 sents a condition that is commonly observed; the odd chromosome is 

 indistinguishable from the others of the equatorial band except for its 

 projecting end which extends well toward one pole. 



In the maturation divisions there is a decided tendency for the 

 nuclear phenomena to proceed independently of divisions of the sur- 

 rounding cytoplasmic mass. This is seen best in smear preparations. 

 Very frequently two or even three large nuclei of the first spermato- 

 cytes may be seen in process of growth or of division in one common 

 cytoplasmic mass which shows no indications of being divided into 

 separate cells. The result is that from four to eight (or exceptionally 

 twelve) spermatid nuclei may ultimately arise in a common syncytial 

 mass. They become set apart in more or less distinct cells only gra- 

 dually during the early progress of their transformation into heads of 

 spermatozoa. Fig. 14 represents a common cytoplasmic mass con- 

 taining the products of the nuclear division of a primary sper- 

 matocyte. It is from a smear preparation and shows the division to 

 have resulted in the production of daughter groups of eight and nine 

 chromosomes respectively, the latter containing the undivided odd. 



The so-called resting condition of the nucleus may or may not 

 occur between the first and second divisions of the spermatocytes. 

 This seems to depend upon the rapidity with which spermatozoa are 

 being generated. At the height of the breeding season in spring it 

 is less likely to occur. Fig. 16 represents such a resting nucleus. 

 It ordinarily contains several chromatin nucleoli but there appears to 

 be no constancy in their form or number. 



While at the conclusion of the first divisions of the spermatocytes 

 eight and nine chromosomes respectively were handed on to the 

 daughter cells, when the latter become ready for the second division 

 a second reduction in numbers has occurred so that in these sper- 

 matocj-tes, as in the corresponding ones of the guinea, four and five 

 chromosomes respectively appear. That is, the eight chromosomes 

 which passed to one end of the spindle in the first division have 

 paired to form four chromosomes, and eight of the nine which passed 

 to the opposite pole have paired similary, the odd remaining unpaired. 

 Fig. 15 represents a smear preparation of four such nuclei* in one 

 continuous cytoplasmic mass. The chromosomes are in late prophase 

 or early metaphase of division and are arranged into two distinct 

 groups of four and two groups of five chromosomes. They have 

 evidently been derived through division from two primary spermatocyte 

 nuclei which lay side by side in the same mass of cytoplasm. 



