HOWELL — THE CALIFORNIA MASTIFF BAT 
115 
the surrounding hairs being moistened by the exudation of a slimy 
matter with a very strong odor. The glands were active in most of 
the males secured March 28, and in but one of those taken December 5. 
By the middle of April the glands have greatly subsided. As far as 
I am aware, all of the European bats which have been dissected and 
examined in this connection, have been found to breed in the fall, or 
at least some time during early winter. The incipient ovule then re- 
mains in a quiescent state in a manner and by a means on which it is 
not necessary here to dwell at great length. The embryo does not 
reach its place of development nor start to form until warmer weather 
and the consequent increase of chiroptine activity stimulate it to grow, 
and this beginning can be retarded for several weeks by keeping the 
prospective mother in a low temperature. There is no reason to suppose 
that most of our bats differ in this respect, although the phenomenon 
probably does not obtain with tropical bats. My experience has led 
me to believe that probably the rut does not begin at the same time 
with all males, but that its start may depend on the animahs condition 
or some indeterminate cause. At any rate, it has been ascertained that 
the rut of some Enghsh bats lasts for a comparatively long time, and fertili- 
zation probably takes place at any time during the winter that op- 
portunity offers. 
Females secured April 15 each contained a single embryo with a 
uniform length of three-quarters of an inch. As I was particularly 
anxious to examine the young and was leaving for the north the first 
of June, I took two females May 31 which were very heavy indeed. 
Had I known that it would be so long before the young appeared, I 
would not have disturbed them, but I had daily expectations while 
they were in captivity, and as they seemed to be perfectly healthy and 
cheerful, I kept one until June 30, when a young one was born, but it 
had then been dead for several days and I could not save it. It was 
surprisingly large and dull black in color. The other female I presented 
to the Museum of Vertebrate Zoology and it died June 14. 
These bats may either hang in a horizontal row, or crowd singly into 
crevices. A favorite position is hanging vertically with the whole 
length of the legs hooked over onto a horizontal surface above, and 
slightly braced by the bend of the wings. They often vibrate the body 
gently for minutes at a time. Normally, the ears are held in the position 
shown in the illustrations, but the eyes are then concealed, so upon 
the slightest disturbance the ears are raised until the upper surfaces 
almost touch each other, and the animal will shrink away as far as 
