482 
J. BRONTE GATENBY. 
spermatozoa of moths are reaction products, probably caused 
by the changes in the chemical properties of the haemolymph 
during metamorphosis. He says : “ In the case of Sarnia it 
is easy to observe, without going into chemical details, that 
the blood in old pupa), which produce the atypical sperma- 
tozoa, has very different properties from those in the young.” 
It must be admitted that there may probably be some truth 
in this plausible explanation ; but, while believing that 
“ apyrene ” spermatozoa may be caused by some subtle 
alteration in the haemolymph, it is well at present to accept 
Goldschmidt’s explanation with caution, and for the following 
reasons : 
(1) In different larvae and pupae of moths and butterflies, 
though individuals may be sub-equal in size, the develop- 
ment of the spermatozoa may have reached much later 
stages in one than in another example. No rigid synchronism 
here holds good. 
(2) In some forms like Spilosoma, all sperm-formation is 
finished by the time the larva is full grown. In other forms 
which appear at the same time and have the same sort of life 
cycle, sperm-formation takes place mainly in pupa). 
(3) Apyrene spermatozoa may be the first kind to reach 
development in the testes. Eupyrenes may only appear 
much later. 
(4) Apyrenes and eupyrenes may be found developing 
side by side at what appears to be the same stage. 
(5) Apyrenes appear in Molluscs where the suggestion of 
altered conditions of a blood fluid would not seem to apply, 
and where no metamorphoses takes place. 
With regard to the statement in paragraph three, the follow- 
ing is my experiment : A number of Pygaera bucephala 
larvae pupated in September. The testes then contained 
only spermatogonia and spermatocytes not quite grown to 
their full size. The pupae were kept in the warm laboratory, 
and near the end of October it was found that the testes con- 
tained several bundles of spermatozoa and spermatids, all of 
which were abnormal or apyrene. About Christmas the 
