454 E. ELEANOR CAROTHERS 



in their actual relation to each other in the sections, then a 

 careful study was made and details filled in when necessary. 

 Later, the chromosomes represented in plate 1 were arranged 

 roughly according to size and placed on the plate so that the 

 transverse rows represent the chromosomes found in one cell 

 while the vertical rows represent the corresponding chromosomes 

 in different cells. The eight complexes shown on this plate 

 are typical of the conditions found in the hundred cells. They 

 are so placed that the accessory is always passing to the upper 

 pole. 



Taking up first the small one at the right (no. 1), which is 

 one of the heteromorphic pairs, we find in five of the cells (b, c, 

 d, f, h) the atelomitic dyad going to the cell which lacks the ac- 

 cessory, while in three (e, g, i) it is going into the same cell as the 

 accessory. The other two heteromorphic chromosomes, num- 

 bers 7 and 8, respectively, are so nearly identical in size and 

 behavior that no attempt was made to distinguish between them. 

 Instead, the segregation of their homologues in relation to each 

 other a ad in relation to the accessory was noted and gave all of 

 the information desired. If these two chromosomes are com- 

 pared with each other in the first four cells (b, c, d, e), it will be ob- 

 served that the dyads with nonterminal fiber attachment are going 

 to opposite poles; in the remaining four cells (/, g, h, i) they are 

 going to the same pole. But in cells / and g they approach the 

 pole which lacks the accessory, while in the last two they will 

 enter the same cell as the accessory. Now, if we compare chro- 

 mosome number 1 with numbers 7 and 8, it will be seen that its 

 dyads also segregate independently of either of the others. For 

 instance, in the last four cells (/, g, h, i) its atelomitic dyad passes, 

 either to the same second spermatocyte as the similar dyads of 

 the larger chromosomes (/ and i), or to the cell which receives 

 the telomitic dyads {g and h). It is evident then that here are 

 four chromosomes (nos. 1, 4, 7, 8) for which this is the segrega- 

 tion division and that they are distributed more or less with- 

 out regard to each other or to the second spermatocytes. 



If there is free segregation, the number of equally possible 

 combinations in the gametes of a single individual is repre- 



