CHROMOSOME STUDIES 229 



ill somatic cells. They argue that if such conditions are found 

 in somatic cells, where only longitudinal divisions occur, the 

 similar heterotypical division of the first maturation may like- 

 wise be interpreted as longitudinal. The second is like it, 

 therefore no reduction occurs. The question of heterotypical 

 division we shall discuss later. Their observations, however, 

 are evidence that we are dealing with at least some transversely 

 segmented, and possibly compound, chromosomes in Amphibia. 



In Lepidosiren Agar ('11, figs. 6, 7) found thirty-eight chromo- 

 somes. Of these, thirty-four are clearly either V's or hook- 

 shaped, four are rod-shaped. He notes a transverse constric- 

 tion across each of the thirty-four univalent chromosomes, as 

 he calls them, and says ('11, '12) that it corresponds in the 

 spermatocyte divisions with the apices of the V's of the somatic 

 or spermatogonial mitoses. This is in exact agreement with 

 my results on Chorthippus. He also shows ('12, p. 291) that 

 for each chromosome this constriction always lies at a certain 

 point, whether the limbs are equal or unequal. This is de- 

 scribed for the five largest chromosomes. One pair always has 

 limbs of nearly equal length in all mitoses, while the four pairs 

 next in size are always hook- or J-shaped. This resembles 

 Chorthippus, where there are always three pairs with arms of 

 unequal length. 



In mammals van Hoof ('12) figures in spermatogonia (figs. 

 01-2, 03-6, to 03-8) and anaphases of the first spermatocyte 

 (plate III, figs. 026-48d; plate IV, figs. 027-50, 01-65, 01-66) 

 rod-shaped, J-shaped, and V-shaped chromosomes. A few of 

 his V's have sharp apices, where they show a constriction. I 

 think that in man, according to the work of Wieman ('13), 

 there is evidence of compound chromosomes in the transverse 

 segmentation, which is clearly shown, and in the presence of 

 many short V-shaped chromosomes. The great disagreement in 

 the number of chromosomes reported for man may be due, in my _ 

 opinion, to the extent of this compounding in chromosomes. 

 Winniwarter ('12) reports forty-seven for a Caucasian, while 

 Guyer ('10) and Montgomery give twenty-two (cf) and twenty- 

 four ( 9 ) for the negro. Wieman finds an intermediate num- 



