46 THE CHICAGO ACADEMY OF SCIENCES. 
To what extent the penis is everted, could not be satisfactorily 
ascertained, but it is believed to be partly protruded. The penis-sac 
probably performs very largely the sexual functions during copula- 
tion, the penis being, in fact, but an enlargement of the vas deferens. 
The length of time of the coitus was not determined; Lymnzas were 
noted in coitu for more than a day, and it is possible that it may oc- 
cupy several days. 
Crosses between different species of Lymnzas have been ob- 
served. Heynemann! records a cross between Radix auricularia and 
Lynnea peregra, the former acting the part of the female and the 
latter that of male. Chaster? records a cross between Lymnea stag- 
nalis and Radix auricularia, the former performing the function of 
the male. The specimens were taken in copulation by Mr. H. E. 
Craven at Litchfield, England. The union was not observed to be reci- 
procal. The progeny were good examples of peregra and the query 
is raised (by Chaster) as to whether peregra may not be the ancestral 
form of stagnalis and auricularia. Recently the writer has observed 
Lymnea stagnalis lilliane and Galba emarginata in coitu. As the 
specimens were not preserved to deposit their eggs, the result of the 
union is not known. 
The eggs of Lymneza are laid in irregularly elongate-ovate, gela- 
tinous masses on stones, sticks, stems and leaves of water plants, on 
other shells, both dead and those occupied by the animal, and, in fact, 
on any kind of debris. The size of the egg masses varies consider- 
ably in the same species as do also the number of eggs in each mass. 
Three egg masses of Galba palustris from Colorado gave the follow- 
ing data: 
Size 16.00 + 4.50 mill; number of eggs 50 
219,50 vaso Oy VSR ieaem se 
A150 ee A peor see 
Galba reficxa from Chicago measured as follows: 
Size 34.50 + 1.60 mill; number of eggs 130 
The embryology of the Lymnzas does not differ radically from 
that of other Pulmonata, excepting in some minor features, notably 
the retention of the velum in post embryonic life. In the trochosphere 
a ring is formed about the developing embryo, which becomes ciliated 
and is used as an organ of locomotion. This is termed the velum, and 
when fully developed the mollusk is said to be in the veliger stage. 
The mollusk retains this velum in post embryonic life, though it loses 
1Nach. Mal. Gesell., I, p. 38. 
2Journ. Conch., IX, p. 282. 
