330 GILMAN A. DREW 
several males will follow the females around by the hour while 
the other males remain entirely inattentive. Usually when a 
male begins to show sexual activity he will follow a single female 
although other females that show similar activities are present 
in the aquarium. Occasionally he may change to another indi- 
vidual but he nearly always returns after a few minutes to the 
one to which he has been paying chief attention. 
A few males have been observed that were so sexually excited . 
they followed individuals around quite indiscriminately. Under 
such conditions I have upon three occasions seen a male catch 
another male and insert spermatophores into his mantle chamber. 
Two of the three instances were between the same individuals, the 
second performance being only a few minutes after the first. In 
each of these cases the male seized made great efforts to get away 
and finally to get hold of the male that was holding him but was 
unsuccessful. Upon killing the male that received the spermato- 
phores, sperm reservoirs were found attached to the base of the 
left gill and to the adjacent visceral mass. Such exceptionally 
active males may copulate repeatedly with a single female. Ina 
few cases this has been carried so far that the female has actually 
been killed. Even after the female has become entirely inactive 
and apparently dead the male may copulate with her several times. 
In one case, a male that had been several days without food, after 
copulating with a weakened female, retained his hold and killed 
her by eating a considerable hole through the mantle. 
The male always uses the same arm for transferring the sperm- 
atophores. This arm, the left ventral, is not greatly modified, 
but a short distance from its tip some of the suckers, especially 
those in the row farthest from the midline of the body, and a ridge 
between the rows of suckers show modification (fig. 4, h). The 
peduncles of a dozen or more of the suckers of the outer row are 
considerably elongated and the sucking dises of a few, (six or eight) 
are greatly reduced in size or entirely absent. In both directions 
from these, the dises become increasingly normal until no modi- 
fication is apparent. The suckers of the row toward the midline 
of the body are somewhat modified, the peduncles being somewhat 
shorter than those of the other suckers in the row, and the suck- 
