325 
1906-7.] Helix pomatia with Paired Male Organs. 
fore probable cases of proterogynous hermaphroditism. The gonad first 
assumes the female condition, in many Limacidae and possibly in some other 
Stylommatophora,* in correlation with which the common duct consists of 
oviduct only, and the penis “ Anlage ” is, for a time at least, suppressed or 
remains rudimentary. 
It is interesting to note that all the cases (with one exception — Collinge’s 
Helix aspersa) of absence or great reduction of male organs]* in the 
Pulmonata have been recorded in genera in which the shell is depressed, 
reduced, or absent — that is, in the most specialised forms. But in the figures 
of these specimens of Limax, Agriolimax, and Vitrina given by Babor and 
Simroth the penis rudiment is invariably found on the wall of the atrium, 
and there is nothing in the figures to show that the penis is formed upon 
the primitive genital (which becomes later — the common) duct. 
Consideration of the abnormalities described in the preceding pages 
leads to the conclusion that the penis develops as an epidermal structure 
which, in the Stylommatophora, is closely associated with, and is secondarily 
carried inwards by, the invaginating atrium. The intimate connection of 
the atrium and penis is especially well seen in the supernumerary organs 
of the specimen of Helix described in the earlier part of this paper (pp. 314 
to 317) and in the example recorded by Bietrix (see above, p. 323). The 
origin of the vas deferens as a diverticulum from the inner end of the penis, 
which only later fuses with and opens into the male part of the common 
duct, is strongly supported by the conditions seen in the specimens described 
by Bietrix and Mangenot (p. 323). In proterogynously hermaphrodite forms, 
* The absence of penis in other Opisthobranchs seems to be attributable to a similar 
cause. For instance, Peck (1887-1890, p. 349) describes specimens of Cymbuliopsis calceola 
in which the gonad is in a state of female activity and there is no penis, and Pelseneer 
(1893, p. 24, footnote 2) gives a similar record in the case of Clio striata . 
Giard (1888) refers to a specimen of Paludina infected with Distomum militare, probably 
a case of parasitic castration, in association with which the penis is reduced ; he attributes 
to a similar cause the occasional absence of penis in specimens of Pterotrachea , otherwise 
showing male characters. 
t Reduction of the female ducts has been rarely observed in the Pulmonata or in any 
other hermaphrodite mollusc (Pelseneer, 1895, pp. 37-38). Schuberth (1892, p. 50) has 
described an example of Helix pomatia in which the oviduct is almost completely atrophied 
for a distance of 36 mm. from the albumen gland, so that it is present above the prostate 
as a mere streak. The anterior portion of the oviduct is, however, fully developed. In one 
or two of the large male examples recorded by Babor the female ducts have undergone 
partial reduction, but were probably formerly present in a fully-developed condition. 
The list of recorded abnormalities in the genital apparatus of Pulmonates, as far as they 
have come under my notice, may be completed by reference (1) to an anomalous specimen of 
Glausilia martensi mentioned by Babor (1900), in which the penis and vas deferens are 
fused so as to form a hoop, and (2) to a specimen of Urocyclus ehlersi , described by Simroth 
(1905), in which occlusion of the opening of the penis into the atrium has taken place, and 
the distal end of the penis has dilated to form a thin-walled spermatophore-sac. 
