NEW TYPES OF CHROMOSOME DISTRIBUTION. 133 



My figures of the male groups (Fig. 5, C, D, E and F } agree 

 both in number and in size relations with those of Montgomery. 

 There are 26 chromosomes, two of which are larger and three 

 smaller than the rest. Although Montgomery's figures in both 

 papers ( '01 and '06) show three small chromosomes, he describes 

 three small ones in the first paper and only two in the latter. 

 The number of chromosomes and their behavior in the first and 

 second divisions give an explanation of the size relations in the 

 spermatogonia. 



The female groups (Fig. 5, A and B) show 28 chromosomes, 

 six of which are distinctly smaller than the others. 



In the first maturation division metaphase, 15 chromosomes 

 are present, four of which can be easily recognized as smaller 

 than the remaining ones and one of the four is decidedly larger 

 than the other three. There is no definite arrangement in these 

 figures. All the chromosomes divide equally, so that accordingly 

 each secondary spermatocyte receives 15 chromosomes, the ar- 

 rangement of which is entirely different. The eleven larger 

 chromosomes form an irregular ring while the four smaller ones, 

 which prove to be the differential chromosomes, form a tetrad- 

 group in the center (Fig. 5, K and L, two side views of the 

 second division, metaphase). Unfortunately no anaphases of 

 the second division were present, but the number and size rela- 

 tions in the male and female groups and the analogy between the 

 behavior here and in Sinea, which is described later, leave no 

 doubt as to the manner in which the tetrad-group separates. 

 The eleven chromosomes in the ring divide equally, while the 

 members of the tetrad-group do not divide, but the group as a 

 whole separates so that the three smaller ones pass to one pole 

 and the larger one passes to the other pole. Two classes of 

 spermatozoa, containing 12 and 14 chromosomes, respectively, 

 are thus produced. Accordingly the 14-chromosome class con- 

 tains three small chromosomes while the 12-chromosome class 

 would have none, as the differential chromosome which goes to 

 this pole is as large as one half of one of the smaller dyads (see 

 Fig. 5, K and L). If the 14-chromosome class meets the egg 

 with 14 chromosomes, three of which are small, we would expect 

 28 chromosomes in the offspring, six of which should be small. 



