160 
GICOFFREY SMITH, 
the material for this study were of a uniform slaty-hlue 
colour, with a white bar on the ends of the tail-feathers which 
was particularly conspicuous when the birds were flying; 
the third (C) in its plumage took more after the dove-parent, 
thougli the dove-colour was dai'kened by a slaty tinge. This 
bird also had the white tail-bar, but was otherwise unmarked. 
The bii-ds lived in my aviary for more than a year; they 
actively courted tlie female pigeons put in with them, and 
two of them (hybrids A and B) were successfully paired off 
with two females, which laid eggs. The hybrid in each case 
assisted in the process of incubation, in the way usual for 
male pigeons, but in both cases the eggs were infertile and 
came to nothing. 
The hybrids were killed in June, 1911, and dissection 
showed that all three had apparently normal genitalia, with 
very hu-ge testes, normal vesiculse seminales containing large 
quantities of spermatozoa, and normal cloacal papillm. 
Tlie spermatozoa examined alive under the microscope 
were seen to be in active movement, though some of them 
were obviously deformed, possessing bead-like thickenings 
along the course of their heads. Slides of the spermatozoa 
preserved with corrosive sublimate and stained with iron- 
hoemotoxylin were obtained, and sections of the testes pre- 
served and stained in the same manner were prepared. For 
the sake of cojnparison similar preparations of spermatozoa 
and of testes sections were made from ordinary male pigeons 
and from male domestic doves. 
'An examination of the smear preparations of the sperma- 
tozoa of the hybrids, as compai’ed with the spermatozoa of 
the nor.nal male pigeon and dove, bi-ought out the remark- 
able fact that besides the hybrid spermatozoa being often 
deformed, the great majority of the undeformed spermatozoa 
fi-om all three hybrids are about twice as long as the sperma- 
tozoa from the normal males of either pigeon or dove. A 
reference to PI. 8, figs. 1-5, representing camera tracings 
of the spermatozoa, will help to bring out this fact. It will 
be seen that the size of the heads of the spermatozoa from 
