764 CLASS XIII. 
a gland is situated, which consists of many long blind sacs that 
unite digitally, whose branches or roots im consequence unite to 
form a single efferent duct. This duct then runs along the inferior 
extremity of another larger gland, elongate, and often ending like a 
tongue; this last was regarded by Cuvisr as the ¢estis, and the 
smaller compact gland as the ovary. An exactly opposite opinion 
was advanced by TREVIRANUS’, which however was contradicted 
by Carus, who found eggs in the first-named gland?. With this 
other observations again were in conflict which proved the presence 
there of spermatozoa. The matter seemed inexplicable, until its 
true bearing was illustrated by the microscopic investigations of 
H. Mrecken’?. The gland which Cuvier names ovary, TREVIRA- 
NUS testis, is both one and the other; it is a double, truly herma- 
phrodite gland; every folliculus is double, and within the external, 
which contains eggs, an internal is enclosed with seed and sperma- 
tozoa in different states of development. The tongue-shaped organ, 
regarded by CUVIER as testis, is a gland secreting albumen, and 
covering the eggs with its secretion. Hence this organ becomes 
tumid subsequently to copulation, as on the other hand the true 
sexual gland, according to Cuvier the ovary, after the time of 
copulation shrinks up*. The penis is a long filiform organ, capable 
of eversion, which in copulation is received within a tube that ter- 
_mninates at the end in a round vesicle®. 
1 Zeitschr. fiir Physiologie, 1. 1824, s. 1—30, Ueber die Zeugungstheile und die 
Fortplanzung der Mollusken. So also PREvost, who found spermatozoa in the compact 
gland. Mém. de la Soc. de Physique et d’ Hist. nat. de Genéve, Iv. v. and Ann. des Se. 
nat. XXX. 1833, pp. 43—59, Pl. 5. 
2 Carus Beitrdge zur genauern Kenntniss der Geschlechtstheile einiger Gasteropoden, 
MUELLER’S Archiv, 1835, s. 487—499, Taf. 12, figs. I, 2. 
3 MUELLER’S Archiv, 1844, s. 484, Tab. xIv. fig. 18. 
4 On this account especially the opinion of CUVIER was contested by M. G. VERLOKEN 
in his prize essay, Commentatio de Organis generationis in Molluscis gasterop. pnewmo- 
nicis, which contains several good figures and accurate descriptions with an historical 
review, very complete up to that time of the different previous observations and 
opinions. Ann. Acad. L, B. 1836, 1837. Comp. also A. Paascu de Gasteropodum 
nonnullorum hermaphroditicorum systemate genitali et wropoético. Berolini, 1842, 8vo. 
5 This vesicle was aleady compared by DesHayES and Prevost to the poche copu- 
lative of insects (see above, p. 266). The last writer established by actual observation 
that the penis in Limnei is received at the time of copulation by the pedicle of the 
vesicle. Moreover the pulmonary gasteropod molluscs present an arrangement which 
is not easy to reconcile with the opinions of STEENSTRUP, whose work we alluded to 
