462 E. ELEANOR CAROTHERS 



10, 11, 12). Passing to the first spermatocytes, the largest four 

 chromosomes (pi. 1, row 1, nos. 9, 10, 11, 12) and the accessory 

 (no. 6) are constantly atelomitic. Nmnbers 2, 4, and 5 are con- 

 stantly telomitic, while nmnbers 1, 7, and 8 may vary from 

 specimen to specimen. 



Since heteromorphism is confined to these three pairs, they 

 are the ones whose behavior in heredity is to be followed. For- 

 tunately, they are clearly distinguishable from each other. 

 Number 1 and number 2 are practically alike in size, but num- 

 ber 2 is always telomitic. Number 1, then, is the only small 

 chromosome which may be hetermorphic or atelomitic (pi. 1, 

 column 1). Again, number 7 and number 8 are practically in- 

 distinguishable in regard to size, but when atelomitic, number 7 

 has sub terminal fiber attachment (pi. 1, column 7) while number 

 8 when atelomitic has nearly median attachment (pi. 3, column 

 8). In case number 8 is atelomitic, it has not been distinguish- 

 ed from number 9, but the essential fact that each is atelomitic 

 is easily demonstrated. 



h. Methods of transformation of chromosome number 7; E-shaped 

 tetrads. As just mentioned, chromosome number 7 when atelo- 

 mitic has subterminal fiber attachment. There are apparent 

 exceptions, however, which for a time caused confusion. In prac- 

 tically every individual there are a few. instances of this tetrad 

 opening out in such a manner that the long instead of the short 

 arms are free. For examples, see chromosome number 7, plate 

 2, row 12, and plate 5, row 33. In the latter instance it is espe- 

 cially eas3' to grasp the situation by comparison with the cor- 

 responding chromosome in the row above, where, if we imagine 

 the free ends brought into contact, the two conditions would be 

 very similar. 



At first thought it may seem to some readers that the long 

 free arms may be due to a shift of fiber attachment. Such a 

 condition is carried in one of the families to be taken up later; 

 e.g., the male used in mating number 14 (pi. 3, row 15) carries one 

 homologue of this seventh pair which has a third position for 

 fiber insertion so that when opening out in the usual way this 

 free end is about twice as long as the tj^pe form. Furthermore, 

 this pair also opens out either way, giving figures such as that 



