764 CLASS XIIT. 



a gland is situated, which consists of many long blind sacs that 

 unite digitally, whose branches or roots in 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 CUVIER as the testis, 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 2 . With this 

 other observations again were in conflict which proved the presence 

 there of spermatozoa. The matter seemed inexplicable, until its 

 time bearing was illustrated by the microscopic investigations of 

 H. MECKEL 3 . The gland which CUVIER names ovary, TREVIRA- 

 NUS testWj 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 4 . The penis is a long filiform organ, capable 

 of eversion, which in copulation is received within a tube that ter- 

 minates at the end in a round vesicle 5 . 



1 Zeitschr. fur Physiologic, I. 1824, s. i 30, Ueber die Zeugungstheile und die 

 Fortplunzung der Mollusken. So also PREVOST, who found spermatozoa in the compact 

 gland. Mem. de la Soc. de Physique et d'Hist. not. de Geneve, iv. v. and Ann. des Sc. 

 nat. xxx. 1833, pp. 4359. PL 5- 



2 CARUS Beitrdge zur genauern Kenntniss der Geschlechlstheile 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. VERLOREN 

 in his prize essay,, Commentatio de Organis generationis in Molluscis gasterop. pneumo- 

 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. PAASCH de Gasteropodum 

 nonnullorum hermaphroditicorum systemate genitali et uropoetico. Berolini, 1842, 8vo. 



6 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 Limncei 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 



