CHROMOSOME STUDIES 249 



their views, there is no such thing as conjugation two-by-two. 

 A continuous spireme is formed anew in the nucleus, and breaks 

 up into half as many segments as there are chromosomes. These 

 segments divide twice longitudinally and are distributed during 

 the two maturation divisions to the spermatids. Both matura- 

 tion divisions are considered to be equational. 



The theory of the Italians cannot be discussed in this connec- 

 tion, since they deny that chromosomes are morphological 

 structures. According to the views of Meves, Fick and Dues- 

 berg, it would be hard to explain how, in a nucleus like that of 

 the one-V-type individual of Jamaicana subguttata, a continuous 

 spireme could break up into just half the number of segments, 

 one of which is destined to give rise to the peculiar V-bi-tetrad 

 (figs. 197-199). This segment in the first place would have to 

 split longitudinally, the daughter threads separating along their 

 whole extent except at the ends (figs. 201, no. 14-16), which 

 would remain in contact up to the beginning of the anaphase. 

 In the meantime, before separation is completed at the ends, 

 one of the daughter threads would have to divide transversely 

 at a point not in the middle of the strand to give segments in 

 length equal to a no. 14 and a no. 16 chromosome (figs. 198 199). 

 This would have to be repeated accurately in all cells of the first 

 spermatocyte. It is highly improbable that such could occur. 

 The theory fails to explain the phenomenon of reduction in num- 

 bers or the formation of this peculiar type of first maturation 

 chromosome. 



In the case of the unequal homologous chromosomes of Acrid- 

 ium and Tettigidea, the fact that the members of the pair sepa- 

 rate from each other in the first maturation division and are 

 distributed each to only one-half of the germ cells is proof that 

 the zygotes of the next generation will be formed with varying 

 combinations of these chromosomes in their nuclei. It is diffi- 

 cult to imagine a continuous spireme being formed in the growth 

 period of the first spermatocyte which should become divided so 

 accurately that it would give rise to segments of the exact length 

 of these abnormal chromosomes which are characteristic for this 

 particular combination and seem to be present in all cells of the 



