LINKAGE OF CHROMOSOMES. I7I 



in the group (Figs. 5-8). I find by numbering the members of 

 the pairs as separate individuals, we have thirty-five chromo- 

 somes here as in the other seven forms. In the later stages of 

 growth, nothing appears to distinguish this form from its fellow 

 No. 589 so we must conclude the rods of the related pairs are 

 not held permanently together but are lost after the spermato- 

 gonial division among the other rods of the complex. 



In /. sub guttata a multiple chromosome appears resembling 

 a V which I believe has been formed by the union of two of the 

 autosomes. These, by continued association, have finally united 

 end to end and we find them forming a V. The members or 

 arms of the V are unequal and, as was noted in connection with 

 the associated rods, can not be mates, since mates are identical. 

 Hence the mates to the components of the multiple must be rods. 

 I numbered and paired the chromosomes in the spermatogonia 

 according to size and found two rods 16 and 14 without rod mates. 

 These correspond with the arms of the V in size and appearance, 

 and as many cells show the same relation, it seems to me they 

 may be so taken. Figs. 30-36. 



The inequality of the parts of the multiple is especially well 

 shown in the first spermatocyte figures. The long arm of the 

 V is linked up with a long rod of approximately the same size, 

 while a somewhat shorter or smaller rod is united with the smaller 

 arm of the V. A slight constriction is to be seen where the rods 

 join the arms of the multiple. 



In determining the count for this species, those individuals 

 having the simple rod type chromosomes, have of course thirty- 

 five in their complex. In No. 503, the odd one in this group, 

 there are thirty-three chromosomes of the rod type plus the 

 multiple which I believe is composed of two of these autosome 

 rods united. This then makes the number for the entire species 

 thirty-five, the same as was found for /. flava. 



The exception in J. unicolor contains two multiples or V's 

 similar to the one found in /. suhguttata. They are apparently 

 formed in the same way and probably of the same two chromo- 

 somes, Nos. 16 and 14, as the difference in the lengths of the 

 arms of the V's corresponds with that in No. 503. In the first 

 maturation division, the V's which compose the elongated ring. 



