484 
J. BRONTE GATENBY. 
stimulate the eupyrene spermatozoa or the eggs or both during 
fertilisation ; or by the liberation of some substance to which 
the eupyrene spermatozoa are negatively chemotactic, they 
may act as an aid in the final disposition of the latter.” 
One remark naturally occurs on reading these suggestions 
It is that the vast majority of the Metazoa have no such 
noteworthy dimorphism in their spermatozoa as these Proso- 
branchs, and they overcome any possible difficulty in the 
nourishment, stimulation, and final disposition of their sperms 
without recourse to any atypic formations. Then why should 
certain molluscs depart from the usual methods in so far as 
to need a special new sort of sperm ? Why should some 
other molluscs not have such special sorts of sperms ? Experi- 
ments have shown that the apyrene spermatozoa degenerate 
sooner or later after undergoing katabolic changes in tlie 
albuminous bodies, that they are not so greatly stimulated 
by decaying tissue as are the eupyrene, and that the eupyrene 
spermatozoa live longer than the apyrene in sea-water (1). 
This all shows that the apyrene sperm lacks the energy of 
the eupyrene, and that it is in this way degenerate. For 
myself until further evidence of a more definite nature is 
brought forward I prefer to believe that these atypic sperma- 
tozoa are degeneration products produced by some altered 
condition in certain cells of the testis. 
Whether these abnormal conditions are due to some altera- 
tion in the fluid nourishing and bathing the sperm-cells, and 
why these conditions should apply to some cells and not to 
others, are problems which in the case of the moths at least 
might be solved by further experiment, in the line already 
indicated. Finally, it should be remarked that Goldschmidt* s 
hypothesis of altered conditions is to be regarded as more 
likely than any sex theory, for I feel convinced that in moths 
these spermatozoa arise out of a state of degeneration, and 
the varying conditions which are undoubtedly to be found 
during the metamorphosis of insects might possibly supply 
the disintegratory stimulus. It has already been pointed out 
where Goldschmidt’s hypothesis seems to me to be weak. 
