398 



GASTEROPODA. 



avoid the wound, retreating into his shell, and 

 performing a variety of evolutions to get out of 

 reach. At length, however, the assailant suc- 

 ceeds, and strikes the point of his weapon 

 into the skin of his paramour at any vulnerable 

 point which may be found. The dart is gene- 

 rally broken off by this encounter, sometimes 

 sticking in the skin, but more frequently 

 dropping to the ground. The reptile Cupid 

 having thus exhausted his quiver, becomes in 

 turn the object of a similar attack, exhibiting 

 apparently an equal anxiety to avoid the threat- 



ening point of the weapon bared against him. 

 At last he receives the love-inspiring wound, 

 and the preliminaries thus completed, each 

 prepares for the completion of their embraces. 

 The other two apertures next dilate, and from 

 one of them issues the long and whip-like penis, 

 unrolling itself like the finger of a glove ; this 

 being fully developed is introduced into the 

 vaginal orifice of the other snail, which in the 

 same manner inserting its penis into the female 

 aperture of the former, both mutually impreg- 

 nate and are impregnated. See jig' 195. 



Fig. 195. 



It is difficult to conceive what can be the 

 use of the dart so singularly employed; it 

 would seem to be an instrument for stimulating 

 the sleeping energies of the creatures to a 

 needful pitch of excitement ; yet why it should 

 be peculiar to the snail is not obvious, for in 

 the slug and other Mollusca certainly not less 

 apathetic, no such structure has been detected. 



In Vaginulus (fig' 189) a similar arrange- 

 ment of the principal organs is observable, 

 although some modifications are met with 

 which deserve our notice. No sac of the dart 

 is found in this animal, but a fasciculus of 

 cceca, analogous to the multifid vesicles as far 

 as their structure is concerned, is connected, 

 not with the female apparatus, as in the snail, 

 but with the male organs. The orifices of the 

 two sexual systems are here separated by a 

 considerable interval, the penis emerging at 

 the side of the neck, near the right superior 

 tentacle at z, while the orifice of the female 

 parts is placed between the cuirass and the 

 mantle, considerably further back. The ovary 

 (ni) is similar in structure to that of the snail ; 

 and its duct, in like manner, forms many 

 convolutions in the substance of the testicle 

 (p), from which it issues, much increased in 

 size, to expand into a large membranous re- 

 ceptacle (<?), corresponding in function with 

 the tortuous matrix of the Helices; this part 

 of the oviduct is filled with an albuminous 

 fluid, and from it runs the narrower canal (r), 

 which may be regarded as the vagina, and 

 which before its termination communicates 

 with a lateral pouch, identical with what has 

 been called the bladder. The testicle (p) ap- 

 pears to consist of two portions, from which 



arises the vas deferens (o). On tracing this 

 tube it is seen to divide into two branches, one 

 opening into the bladder (s), an arrangement 

 to which we shall again have occasion to revert, 

 whilst the other runs fonvard to the root of the 

 penis (w). The latter organ presents two por- 

 tions, a long tubular coecum (u), resembling 

 the corresponding part in the snail, and a 

 thick muscular cavity, from which the former 

 arises as a kind of appendage ; on opening the 

 thicker portion its interior is seen to be rugose, 

 and to enclose a small body, something like 

 the caput gallinaginis in the human urethra. 

 The multijid vesicles (j/) open near the exterior 

 orifice, through which the whole apparatus, by 

 a process of inversion already described, is 

 protruded so as to form the male organ of ex- 

 citement. 



In many of the Tectibranchiata a remark- 

 able arrangement of the generative organs is 

 found, as the male viscera are divided into two 

 distinct portions, the exciting organ being at 

 one extremity of the body, while the testis is 

 found connected with the female apparatus in 

 a distant part of the system. This will be 

 seen in Doridium Meckelii (Jig- 196); the 

 penis (/), seen retracted in the figure, issues 

 from the side of the neck, and has appended 

 to its root a zig-zag tube, inclosed in a mem- 

 branous canal, the nature of which is un- 

 known. Quite detached from these, and 

 placed near the anus, we have the matrix (f) 9 

 the testis (g), and the bladder (i), occupying 

 their usual relative position as regards each 

 other, and terminating in the vulva or sac of 

 generation (//). 



In Aplysia the organ of excitement is found 



