416 Mr. H. A. Baylis on 
form a groove extending from the cloaca to the tip of the 
tail. Some of the papillz are not infrequently carried over 
so as to lie on the inside of this groove, and are thus only 
seen with some difficulty. In any case, however, the number 
on each side does not seem to be constant. 
The same remarks apply, on the whole, to the material 
from the South Shetlands, the infolding of the sides of the 
tail (fig. 2B) being often very marked. In this case the 
Jargest number of papillee counted was eleven on the right 
side and eight on the left. The tail is laterally compressed 
in both forms, and slightly asymmetrical, the right side 
tending to be a little longer than the left. This is probably 
Fig. 5. 
C. crassicauda ; views of the caudal ends of two pairs of individuals, to 
show the position during copulation. 
a peculiarity connected with the mode of copulation, which is 
well seen in the material sent by Mr. Bennett. Several pairs 
of individuals have remained, on fixation, in the position 
indicated in fig. 5. The manner in which the tail of the 
male is coiled round the constricted portion of the female is 
apparently constant. The tail makes two or three turns in 
the direction of a right-handed screw, but the last turn is 
reversed, so that the tip of the tail comes to lie in front of, 
instead of behind, the previous coil. This seems to offer an 
explanation of the slight asymmetry of the tail. Though 
Creplin noted the constriction in the region of the vulva, 
and speculated as to the probability of its being a natural 
