528 QASTEKOPODA. 



when uninverted (for it must be turned inside out in order to expose the 

 weapon within it), is a thick muscular bag (fig. 264, a'} ; and on open- 

 ing it, it is found to contain the dart, attached to a nipple-like pro- 

 tuberance at the bottom of the sac. The dart itself is four-sided ; and 

 as it grows by the constant addition of calcareous particles deposited at 

 its base from the surface of the vascular protuberance to which it is 

 fixed, so, if broken off, it is speedily reproduced in a similar manner. 



(1392.) The male part of the generative system is composed of a 

 testicle, vas deferens, and the whip-like penis above described. 



(1393.) The testicle is considered by Cuvier* to consist of two distinct 

 portions : one, a soft whitish oval mass (fig. 264, p) ; while the other is 

 elongated, thin, and granular (y), being imbedded among the convolu- 

 tions of the oviduct (w). The vas deferens forms the excretory duct of 

 both these portions, and terminates in the side of the penis, its orifice 

 becoming, of course, external when that organ is protruded by evolution. 

 The intromittent organ itself, as seen when lodged within the body of 

 the snail, consists of two parts, a muscular bag which forms its body (6'), 

 and a long whip-like portion (z) ; the latter is hollow, but not perfo- 

 rated. The reader will now have little difficulty in understanding how 

 this remarkable apparatus is protruded. The generative sac, common to 

 both the male and female organs, first becomes inverted ; the body of 

 the penis (&') then undergoes inversion in a similar manner, so that the 

 orifice of the vas deferens appears externally; and lastly, the long 

 appendage to the penis (z), being likewise turned inside out by the action 

 of the muscles that compose its walls, completes this strangely-con- 

 structed instrument. Its subsequent retraction into the visceral cavity 

 is effected partly by the assistance of a special retractor muscle, which 

 acts upon the body of the penis, but principally by the same contrac- 

 tility that accomplished its evolution. 



(1394.) The female system next demands our notice ; and this will 

 be found to present for our investigation an ovary and lengthy oviduct, 

 to which are appended certain auxiliary organs, namely the spermatheca 

 and the multifid vesicles. 



(1395.) The ovary (fig. 264, s) is found situated in the inmost re- 

 cesses of the shell, and partially imbedded in the substance of one of the 

 lobes of the liver. From the ovary a long oviduct (q) is derived, which 

 is at first thin and slender, but, soon becoming wider and more capacious 

 (u), it gradually expands into an extremely convoluted intestiniform 

 viscus, to which the name of uterw has been improperly given, and 

 ultimately terminates in a canal derived from the spermatheca, to be de- 

 scribed hereafter. It is during their passage through this enormous 

 oviduct that the eggs attain their full growth preparatory to their 

 expulsion from the body. 



(1396.) Another viscus, called by Cuvier simply " the bladder," is, 



* Loc. cit. 



