LINKAGE OF CHROMOSOMES. 165 



In the first spermatocyte stages the chromosome complex 

 consists of seventeen undivided autosomes plus the accessory or 

 sex-chromosome ([Figs. 10 and 11). As division proceeds, the 

 unpaired sex-chromosome goes entire to one pole accompanied 

 or followed by 17 autosomes. The mates of these seventeen 

 autosomes pass to the opposite pole, thus making the number at 

 the two poles eighteen and seventeen respectively. Before this 

 division takes place, the paired autosomes show the same grada- 

 tion in size as was noted in spermatogonial figures (Fig. ii). 

 There are several extremely large chromosomes in this individual 

 but the change in the series is so gradual that it is difficult to 

 say where the dividing line falls. However, I am reasonably 

 sure I can pick out at least three pairs in the spermatogonial or 

 three undivided chromosomes in the first spermatocyte cells, 

 that are larger than the others. 



In 588, the second individual of /. flava studied, a slight but 

 distinct difference can be noted in the spermatogonial figures. 

 The number of chromosomes is the same, thirty-five, and all are 

 of the rod type varying in size as was noted in No. 589. How- 

 ever, in pairing off the chromosomes, I find there are in each cell, 

 two pairs of closely related ones. Each member of the pair No. 

 16 is always found in close association with a member of the 

 pair No. 14 {A, Figs. 5, 6, 7, 8). The members of the other pairs 

 are distributed throughout the figure very much the same as in 

 corresponding figures of No. 589. The largest chromosomes 

 always appear on the periphery and the smallest ones in the 

 center. These two sets of parallel rods, as may be noted, in the 

 figures, have no regular position in respect to each other or to 

 other chromosomes in the cell. Sometimes they are near each 

 other and as often they are to be found on opposite sides of the 

 figure. However, they are never far from the accessory chromo- 

 some. 



Jamaicana subguttata Walker. 



Five individuals' out of six belonging to /. subguttata show 

 only the rod type of chromosomes. In the sixth individual, a 

 distinct variation is found in the appearance of a V-chromosome. 



Of the ten individuals I studied, numbers 416, 585, 586, 587, 

 438 and 503 belong to Jamaicana subguttata. The sections of 



