CHROMOSOME STUDIES 219 



with a similar long-rod chromosome and the short limb with 

 a similar short-rod chromosome. There would then result in 

 first maturation divisions a long V with unequal limbs, exactly 

 what is found (figs. 198, 199). At the end of this division the 

 limbs of the original spermatogonia! V separate from their rod 

 mates and the V, passing to one of the second spermatocytes, 

 has the same size as a spermatogonia! V. 



In two-V type individuals, first spermatocytes show the sex 

 chromosome, fifteen rod-shaped tetrads, and an elongated ring 

 (fig. 201). This ring evidently results during the exconjugation 

 process of the pair of V-shaped chromosomes. The longer (16, 

 16) and shorter (14, 14) sides of this ring probably contain the 

 same elements as are present in the longer and shorter limbs of 

 the first spermatocyte V's of figures 197 to 199. I have ex- 

 amined carefully every cell drawn by Woolsey and am reasonably 

 certain that in Jamaicana we have cases of linkage of non- 

 homologous rod chromosomes to form V's, etc., which are en- 

 tirely similar in their behavior to the V's of Chorthippus. Jamai- 

 cana is important because it shows the transition from rod-shaped 

 to V-shaped chromosomes and a corresponding reduction in the 

 number of chromosomes, not only within the genus but within 

 each species. It shows in the individuals studied that two chro- 

 mosome pairs may exist as four rods, or as two rods, and one V 

 or as two V's. At the same time there are present in each 

 case thirty additional rod-shaped chromosomes and the sex 

 chromosome, making always thirty-five rod chromosomes or their 

 equivalent. 



DISCUSSION 



1. Y-shaped chromosomes 



1. General. I undertook an examination of the V-chromo- 

 somes of Chorthippus in an attempt to find if such V's were not 

 in some way concerned in bringing about the smaller number, 

 seventeen, which all species of this genus seem to have. The 

 number characteristic of the subfamily to which this genus 

 belongs, as well as of the two other subfamilies closely related 



