NEW TYPES OF CHROMOSOME DISTRIBUTION. 145 



spermatogonia and 16 in the first division, ten of these must be 

 bivalent and six univalent. While I have not seen the anaphases 

 showing the division of the three small chromosomes, it seems 

 very probable that they and all the others divide equally in this 

 division. The fact that 16 chromosomes are present in the 

 equatorial plate of the second division, supports the above con- 

 clusion (Fig. 10, L, M and N ; in L and M, the large chromo- 

 some which lies below the five in the middle, could not be shown). 

 The chromosomes in the group of three formed by the large one 

 and two others, lag behind and are the last to divide (Fig. 10, 

 A', a side view of the first division, anaphase). 



The metaphase plate of the second division again shows a 

 regrouping of the chromosomes, similar in arrangement to those 

 already described, but differing in the number of elements which 

 compose the central group. Ten of the chromosomes form an 

 irregular ring, within which are the other six, forming a hexad 

 group (Fig. 10, N), composed of the three small chromosomes, 

 the large one and the two which were linked with it in the first 

 division. The three small and two medium sized ones lie ap- 

 proximately in one plane, while the large one lies a little above 

 or below these five, on the other side of the equatorial plane. 

 Unfortunately no side views of the metaphase showing all six 

 members of the hexad group, were present in my material. The 

 small chromosomes are so very minute at this stage that they 

 are with difficulty seen at all. The chromosomes in the ring 

 divide equally, while the members of the hexad group do not 

 divide individually, but the group separates so that the large 

 one passes to one pole and the remaining five to the other. 

 Anaphases showing a clear demonstration of this separation were 

 not present in my material. If there is any doubt as to the 



view of the first division, anaphase, showing the late division of the complex ; 

 L-N, metaphase figures of the second division, showing the ring of ten bi- 

 valents and the univalents in the center in M and N only five of the uni- 

 valents are shown, as the large one lies beneath ; O, side view of the second 

 division, anaphase. showing the manner of separation of the large and two 

 medium sized univalents one small one is also present. No anaphases, show- 

 ing the distribution of the three small univalents, were present. P, anaphase, 

 polar view of the second division, showing the two medium univalents, and 

 two of the small ones ; O, anaphase, showing the large univalent going to 

 one pole. The enlargement is 4,018 diameters. 



