434 Moore. — Essential Similarity of Chromosome 
in respect to the last division of the spermatogenesis differed 
entirely from that given by Hertwig 1 ; in fact, the phenomena 
as described by Brauer come, as we shall see, exactly into 
line with the corresponding processes in plants. 
Now it is extremely unlikely that Brauer would criticize 
this point in Hert wig’s work, unless he were quite sure that 
the process of maturation in the sexual cells of Ascaris went 
forward in the manner he describes, but if it is true that 
it does, it is also tolerably obvious that the modern work 
which is said to have supported the universal existence of 
a £ Reductionstheilung,’ rests on a false foundation. 
Contemporaneously with Brauer 2 , I had been working on 
the same phenomena in mammals, and although fully expect- 
ing to confirm the existence of a e Reductionstheilung,’ the 
more I became acquainted with the maturation of these cells, 
the more I was convinced that no reduction of this kind 
really occurs. 
If there is one histological feature of mammalian sperma- 
togenesis more marked than the rest, it is the division ter- 
minating the individual existence of the ‘ growing cells,’ which 
are known under several different names in the literature 
dealing with them. Now the division of these cells is, as 
I have shown, a normal mitosis, and is carried out in the 
peculiar manner for which Flemming used the name of 
‘heterotypic.’ Further, there are peculiarities in the pro- 
phase of this division which, together with the great size of 
the cells, and the fact, that among Mammals, just as in 
Amphibia, Elasmobranchs, and Birds, it is invariably pre- 
ceded by a more or less extended series of ‘ homotype ’ 
divisions, render it evident that throughout the above 
enumerated types, the advent of the great heterotype 
division constitutes a corresponding and homologous stage 
in the development of their respective sexual cells. 
In the spermatogenesis of these animals, the heterotype 
division forms, so to speak, a landmark which is common 
1 Loc. cit. 
2 Loc. cit. 
