81 



THE FEMALE ORGANS OF NERITINA FLJJVIATILIS. 



By G. GiLSON, 



Professor of Zoology at the University of Louvain. 



Read \Zth March, 1896. 



Amongst the multifarious dispositions of the genital ducts met with 



in Gastropoda, one of the most interesting is that in which the 



copulatory organ is separated from the duct of the gonad. In Clio, 



for instance, the penis is situated at some distance from the genital 



opening, an epidermal groove forming the only connection between 



the two. In Boris, the copulatory vesicle is connected internally 



with the female part of the hermaphroditic system, but has a separate 



opening on the surface of the body.^ 



So far as I am aware, however, no case of a separation between 

 the copulatory and reproductive organs has yet been described in 

 the female system of a dioecious type. I have thought it worth 

 while, therefore, to call attention to the fact that such a disposition 

 is realized in Neritina flimatilis, especially as Claparede's classical 

 monograph^ on the anatomy and development of the genus contains 

 an entirely erroneous description of the organs in question. 



According to Claparede's description, the female system is very 

 simple, and presents no special interest. It consists (Fig. I, which 

 is a reproduction of one of Claparede's drawings) of an oviduct {h) 

 provided with an enormous glandular dilatation {a), followed by 

 a muscular "uterus" (/) with two appendicular vesicles or 

 receptacula {c). The system was thus supposed to have only one 

 aperture of communication with the exterior, serving both for 

 copulation and oviposition. Claparede believed the eggs to pass 

 down through the oviduct into the glandular dilatation, and that 

 from this they passed through a narrow portion of the general 

 duct into the "uterus," to be deposited after being surrounded with 

 albumen and shell. 



The structure of the female ducts is, in fact, as follows : — The 

 gonad (Fig. II, ov.) gives origin to a narrow tortuous oviduct {d). 

 This soon divides into two branches, which open separately on to 

 the exterior. These two branches are very different in structure 

 and function. One of them we must regard as the main part, 

 the normal base of the oviduct; and it terminates in what we 

 may call the incubatory chamler {d.i.). The other {d.c.) is an 

 accessory duct, and ends in what may be termed the copulatonj 

 \chamber or bursa (h.c). The incubatory chamber is continuous with 

 an enormous dilatation of the oviduct, the thick wall of which 

 t contains very remarkable glandular cells, which secrete an albuminous 

 product. This portion (d-ff.) may be termed the glandular segment 



1 See P. Pelseneer, " Introduction a Tehule des Molhisques." Bruxelles, 189-t. 

 1 ^ Claparede, " Anatomie und Eutwickehiugsgescliiclite der Neritina Jiuviatilis'''' : 

 IMiiller's Archiv. 1857. 



