480 
J. BRONTE GATENBY. 
like mitochondria tend to become fused fan-wise from the 
zone of influence of the centrosome. It is nevertheless quite 
true that the mitochondria, though often so affected, almost 
invariably in later stages keepwell outside the amphiaster. 
This seems to show, as well as much other such evidence does, 
that the mitochondrial granules are not absolutely equally, 
but only approximately equally divided. It is quite certain 
that the mitochondria are never divided in such a correct 
manner as the chromosomes . 1 Some stages given by me 
elsewhere show that this approximately even division of the 
mitochondria may be departed from, resulting in a very 
perceptibly uneven distribution. Even if the suggestion of 
two special capital centres of force in the spermatid be not 
completely substantiated, it is quite certain that spermio 
genesis is the sum result of the separate workings of a 
number of forces, and these latter, when not working in 
unison, produce abnormal spermatozoa. The curious sper- 
matogenesis of some hybrids might be traced to a want of 
unison in the arrangement of the elements provided by both 
sides. It has been suggested that the growth of tlie sperm- 
tail depends upon the head centrosome. Whether this applies 
to the alteration of shape in the nucleus and acrosome is, 
indeed, difficult to say. The nucleus, after losing its place 
at the sperm-head, is still able to become elongate, and the 
same remark applies to the acrosome. 
The main conclusion is that even though certain cell 
elements in spermatogenesis become degenerate, others may 
be able to go further on with apparent semi-independence, 
and may even become normally formed. 
The Degenerate Spermatozoon as a Probable 
Special Sex Determinant. 
Hertwig ( 6 ) suggested that the “ apyrene ” spermatozoon 
might by fertilising an egg produce offspring of a different 
sex from an egg fertilised by a “ eupyrene ” sperm. Other 
1 See, however, E. B. Wilson on Centrums, ‘Nat. Acad. Sciences,’ 
yol. 2, June, 1916. 
