294 T. H. MORGAN 



that two kinds of males are found that differ from each other m 

 the relation of the small x to the large X chromosome — in one 

 kind of male the two remain in contact, in the other the two keep 

 apart. And I pointed out that all of the spermatocyte cells of 

 a given individual show one or all show the other relation. This 

 is in accord with the assumption of two kinds of males that arise 

 when the polar body is eliminated. 



In some of the preparations showing anaphase figures in 

 this species, one of which is redrawn here in plate 1, figure o, 

 the two lagging chromosomes appear unequal in size. In other 

 figures, however, (figs. 5, 6, 21, of my 1912 paper) the two lag- 

 ging chromosomes appear to be equal or subequal. For this 

 reason I stated ('12) that the two equal chromosomes represent 

 one large sex chromosome divided into halves. On this view the 

 conjugating pair of small x's have been separated and moved to 

 their respective poles while only the large X lags as it passes to 

 the outer pole. 



It will be noticed that superficially the number of chromo- 

 somes in P. fallax is double that in P. caryaecaulis. This sug- 

 gests that the group in P. fallax represents the double number 

 of chromosomes of caryaecaulis (tetraploid) , or that carj^aecaulis 

 is P. fallax halved. But if the full number of chromosomes in 

 P. caryaecaulis is looked upon as eight, this relation does not 

 hold, unless one supposes that there are four small chromosomes 

 present also in P. fallax (giving sixteen in all) that are attached 

 permanently to other chromosomes. From this point of view the 

 chromosomes of the one species would be double the number of 

 the other and P. fallax would become XX and XY, while P. 

 caryaecaulis would become X and Y. In other words the small 

 chromosomes would no longer be reckoned as factors in the sex 

 scheme. I have preferred, however, the interpretation given in 

 the diagram because the two small chromosomes conjugate in the 

 male egg when the large sex chromosomes conjugate; and, again, 

 because one of them lags in the first spematocyte division along 

 with the lagging X. But the latter relations may be only a con- 

 sequence of the first, and be due to the absence of a mate at this 

 time. Still, since it goes into the female-producing sperm, and 



