LYMNZIDAZ OF NORTH AMERICA. 45 
when equal quantities of both species were placed in the aquarium, 
they chose the latter species first. 
j. REPRODUCTION AND NIDIFICATION. 
The Lymneas are sexually hermaphrod‘tes. Unlike the helices, 
they are capable of mutual union, each playing the part of male to 
the other. This is possible owing to the wide separation of the male 
and female orifices. Not only may two individuals perform the act 
of copulation at the same time but three or more individuals have 
been observed in coitu, one individual performing the part of both 
male and female with two other Lymneeas. 
That Lymnza is capable to some extent of self impregnation is. 
apparently proven by Braun* who isolated Radix auricularia when 
hatched. One year later each of three isolated individuals produced 
respectively one, four and five egg masses, several of which hatched 
out young auricularias. 
The copulation of Lymnea stagnalis lilliane was recently ob- 
served and the following notes were made: The penis-sac is everted 
its whole length and appears as a very large, flat, elongate-triangular 
organ. When in coitu the male organ is firmly attached to the female, 
requiring a very strong pull to dislodge it. During the orgasm regular 
pulsations may be seen following the course of the vas deferens, the 
penis-sac being so transparent that this organ may be plainly seen 
occupying a long loop, folded longitudinally. The penis-sac is much 
more swollen during copulation than when observed in a dissected ani- 
mal. During coition the male remains quiescent, with tentacles drawn 
inward and head much contracted. The female, however, seemingly 
pays little attention to the operation, but crawls about eating or exam- 
ining the surroundings with her tentacles. When pulled apart and 
separated, the male immediately seeks the female again, if in the vicin- 
ity, or if placed near another individual, proceeds to search for the 
female opening at the base of the neck. The male is frequently 
found on the shell of the female. 
Lymnea stagnalis lilliane, Galba emarginata and Galba lanceata 
have been observed copulating, and, curiously enough, emarginata, 
though a much larger animal, tried several times to copulate with 
lanceata, showing that at this period (the last of August) the sexual 
instinct is so strong that even distinction between species is lost. This 
was also observed to be the case with stagnalis and emarginata. 
%Nach. Deutsch, Mal. Gesell., XV, p. 146. 
‘ *The terms male and female are here used simply to identify the imme- 
diate sex individuals, as Lymnaea is hermaphroditic, carrying the organs of 
both sexes in the body, as already explained. 
