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Sidney I. Kornhauser 
C. Comparison of the Second Spermatocyte Division of Enchenopa 
binotata and Enchenopa curvata. 
In E. Unotata all the second spermatocytes contain ten chromosomes, 
wliich divide concomitantly. Each spermatid receives ten chromosomes, 
one of which owes its origin to either the x- or the ?/-component of the 
allosome pair. A deeply staining chromosome is present in each spermatid. 
In E. curvata half the second spermatocytes contain nine, the other 
half ten chromosomes. AU these chromosomes divide and there thus 
arise two classes of spermatids, those with an a:-chromosome and those 
without this element. Half the spermatids show a deeply staining chromo- 
some when the other chromosomes have become gramdar. 
The second division in both species is equational or homeotypic, and 
the plane of division of the chromosomes corresponds to the longitudinal 
division first seen in the formation of the tetrads in the early prophase 
of the first spermatocyte and again evident in the anaphase of the first 
maturation division, this plane being at right angles to the first plane 
of division. 
^Vhile the formation of two classes of spermatids is more evident 
in E. curvata than in E. Unotata, the history of the xy pair of E. Unotata 
leads to the conclusion that here, also, two categories of spermatids are 
forme d. 
X. Discussion. 
A. Syndesis and the Maturation Divisions, 
The importance of the study of the chromosomes in maturation 
rests upon the foUowing assumptions, partly theoretical and partly ob- 
servational; 1. that the chromosomes are the bearers of hereditary qual- 
ities (Roux-WeiSjviann); 2. that the inheritance of a sexually produced 
animal is dual and that certain portions, at least, of this inheritance can 
be resolved into units, which are paired and usuaUy behave indepen- 
dently of each other, being segregated in accordance with the law of pro- 
babUity at the time of the production of gerni cells (Mendel); 3. that 
the chromosomes of a single germ ceU are qualitatively different from 
one another (Boveri, Wilson); 4. that two homologous sets of chromo- 
sonies are brought together in the production of a zygote, one set maternal, 
the other set paternal (Montgomery); 5. that there is genetic conti- 
nuity of the chromosomes from cell generation to cell generation of the 
germ ceUs through all the s iccessive generations — oögonia and oöcytes, 
spermatogonia and spermatocytes — (Boveri, Sutton); 6. that in the 
