176 



MONTGOMERY — A STUDY OF THE CHROMOSOMES 



together would correspond to the fifth bivalent chromosome of condition 1). To deter- 

 mine which of these conditions is the more usual, I counted the number of chromatin 

 elements seen on pole views of the monaster stage of the first maturation division. These 

 counts wen; made on spermatocytes from five different testes, and may he condensed into 

 the following table : 



PBEPABATION NO. 



ek;iiT ELEMENTS. 



SEVEN ELEMENTS. 



86 



238 

 408 

 410 

 350 



4 

 6 

 2 

 1 

 



33 



12 

 1 

 9 



23 



Total = 



13 



78 



Thus those spermatocytes with seven chromatin elements would seem to be the more 

 frequent condition. In both cases there is one univalent chromosome, which represents 

 the odd chromosome of the spermatogonia; hut why in cells of the second condition two 

 chromosomes should remain separated instead of combining to form a bivalent one, as they 

 do in the first condition, I cannot explain, unless perhaps the presence of the odd uni- 

 valent chromosome may in some way disturb flu; union into pairs of the ten other chro- 

 mosomes during the synapsis. 



in those eases where there arc sevetrchromatin elements in the equator of the first 

 maturation spindle, the metakinesis results in the division of all the elements; this is a, 

 reduction (transverse) division of the bivalent chromatin nucleolus and of the live bival- 

 ent chromosomes, hut in what plane the univalent chromosome divides could not he de- 

 termined. Only one case was seen where the univalent chromosome was left undivided 

 in the equator after the daughter elements of the six other elements bad reached opposite 

 poles of the spindle. Thus it, would seem that in this division, in the cases where there 

 are seven elements present, all the elements become divided; how if is in tin; cases where 

 there are eight elements could not, he determined. In the spermatid are found either six 

 chromosomes (Fig. 117) and one chromatin nucleolus (IV. 2), or live chromosomes and 

 one chromatin nucleolus. This would show that, the chromatin nucleolus and five chro- 

 mosomes (the derivatives of the original live bivalent ones) divide in the second matura- 

 tion division, but that the sixth chromosome, the derivative of the originally univalent 

 one, does not divide; hut passes undivided into one of the two spermatids. Thus the 

 valence of the seven (dements in these generations would be : first spermatocyte, one 

 bivalent chromatin nucleolus, live bivalent chromosomes, one univalent chromosome; 



