290 FERNANDUS PAYNE 



accounts for the difference in the size of the chromosomes in the 

 different figures. I lay emphasis on the spermatogonial and 

 oogonial counts, as here is part of the evidence which demon- 

 strates that the large end of the unequal pair and the single 

 unpaired chromosome always go to the same pole in the first 

 spermatocyte d. vision. Polar views of the first maturation divi- 

 sion show clearly 12 chromosomes (fig. 1, K, L, M). The single 

 unpaired chromosome can usually be distinguished by its shape 

 (fig. 1, K, L). The unequal pair can also be detected by chang- 

 ing the focus. In side views the two are always easily recog- 

 nized, the single chromosome by its shape and position, the 

 unequal pair by the inequality of its parts (plate 4, A to E). The 

 single chromosome is seldom seen in the metaphase plate, but to 

 one side of it. So far as my observations go, this is the same 

 'side on which we find the large end of the unequal pair. One 

 hundred and fifty counts of metaphase plates show this to be 

 the case. It may even have reached the end of the spindle 

 while the other chromosomes are in metaphase. While there is 

 no definite grouping of the chromosomes in this division, the 

 unequal pair and the single chromosome lie somewhere near the 

 center of the group. All the chromosomes, except the single 

 unpaired one, divide in the first division. The unpaired member 

 passes to one pole undivided and always goes to the same pole 

 as the large end of the unequal pair. As previously stated, this 

 distribution of the chromosomes causes two kinds of secondary 

 spermatocytes. These secondary spermatocytes are alike in that 

 each receives one-half of each of the ten equal bivalent chromo- 

 somes. They differ in that one receives the single unpaired 

 chromosome and the large end of the unequal pair; the other 

 receives the small end of the unequal pair. This also makes a 

 difference in number, one receiving 12 chromosomes, the other 

 11. Figure 1, N, 0, P, are three figures, side view, of an early 

 .anaphase plate taken at different levels. They show most of 

 .the chromosomes divided, the early division of the unequal 

 pair, and that the single chromosome has reached the end of the 

 spindle. Chromosome counts of the second maturation division 

 confirm this method of distribution. Some have 12 chromo- 



