323 
1906-7.] Helix pomatia with Paired Male Organs. 
Klotz, it seems to be produced by a process of splitting from the penis 
rudiment. 
The condition of the supernumerary penis and vas deferens in the 
abnormal Helix indicates that the penis arises from the epidermis as a solid 
or hollow ingrowth which has been secondarily carried inwards by the 
invaginating atrium. Its development would be difficult to explain if the 
penis were differentiated from, and dependent for its origin upon, a primitive 
mesodermal sexual duct, as held by Brock, for there is no trace whatever of 
any such duct on the left side of this Helix. The supernumerary vas 
deferens probably arose in the normal way as a diverticulum from the inner 
end of the penis. 
The origin of the penis from the epidermis is in agreement with its 
phylogenetic history, which points to its appearance as an elevated 
epidermal organ, at first non-introversible and grooved, but later intro- 
versible and tubular, and also better accords with other observations upon 
abnormalities in the Pulmonata than would the origin of the penis from 
any part of the female or common sexual ducts. Bietrix (1886) records a 
specimen of Helix pomatia in which the genital apparatus is divided into 
three quite separate portions: (1) the ovotestis and albumen gland, (2) the 
dart sac and mucous glands, and (3) the penis and its annexes. The penis and 
flagellum are quite normal,* but the vas deferens is represented by a short 
csecum 4 mm. in length. The atrium appears to be a single swollen prolonga- 
tion of the penis sheath. Mangenot (1883) describes a specimen of Helix 
pomatia in which the external genital aperture is closed, in consequence of 
which the atrium and vagina are much dilated by imprisoned fluid contents. 
The atrium is somewhat oval in shape, and the vagina and penis open into it 
at opposite ends of its longer axis. The penis has the usual form and size, 
but the vas deferens is a slender csecal appendage 6 mm. long, arising from 
the inner end of the penis. The vas deferens, which bears a flagellum of 
approximately normal size, has no connection whatever with the common 
duct, and the only connection between the penis and the vagina is the purely 
secondary one afforded by the atrium. Both these cases indicate that the 
penis arises quite independently of the common duct or the vagina, and 
that its development is, in Helix , closely associated with that of the atrium. 
That the penis “ Anlage ” in some cases fails to develop seems to be 
indicated by the recorded examples of absence of the male sexual organs in 
the Pulmonata. Such a defect is more readily understood if these organs 
arise from a separate “ Anlage ” than if they form an integral part of the 
* Except that the retractor muscle is represented by two strands with separate origins, 
hut these unite so that the muscle is single at its point of insertion on the penis. 
