NOTES ON THE GENITALIA OF LYMNZEA. 
FRANK COLLINS BAKER. 
INTRODUCTION. 
WrrH the exception of Lymnea megasoma and Lymnea 
mighelst, nothing has been published on the genitalia of the 
American species of Lymnza. Last fall the writer embraced 
the opportunity to dissect most of the common eastern Lymnzeas, 
with some interesting results which are presented in the follow- 
ing paper. 
In studying this subject it is eminently desirable that the 
material should be freshly killed and not alcoholic, as the latter 
condition causes portions of the 
genitalia to contract and otherwise 
lose their normal shape. Likewise 
in observing the male organ it is, 
essential that it should be fully in- 
verted, otherwise the form of the 
penis-sac and the length of the 
penis will be much modified, as 
shown by the accompanying cut 
(Fig. 1). The genitalia of the nine 
species examined are comparatively 
uniform, differing principally in the 
form of the prostate and in the 
length of the penis. The vagina 
and uterus also show some modifica- 
tions. 
The material dissected was ob- 
tained from the following sources: 
L. stagnalis appressa, stagnalis jug- 
VD 
VD 
p 
P 
PS 
PS 
A B 
Fic. ı.— Male organs of Lymnza. a, 
penis partly everted in penis-sac ; 4, 
fully inverted. Note the different mad 
the penis-sac in the two conditions 
ularis, elodes, and humilis were collected in Braddock's Bay, 
Lake Ontario; Z. emarginata and catascopium were collected 
665 
