ORGANS OF GENERATION IN THE INVERTEBRATA. 99 



however, as the annelida, the acephalous, and gasteropodous mol- 

 lusca, both sets of organs are placed on the same individual, con- 

 stituting it an hermaphrodite. Some of animals of this class, as 

 the holothuriae, possess the power of self-impregrmtion, whilst 

 others, though possessing double organs, require mutual impregna- 

 tion ; this is the case with the leech, and the common earth-worm. 

 In all the insect tribes the sexes are separate, the male organs being 

 the testicles, the vesiculae seminales, the excretory tubes, and in 

 many, the prehensores.or organs for seizing the female during 

 coitus. The female organs consist of the ovaria, the oviducts, the 

 spermotheca, or receptacle for the male semen, and the ovipositor, 

 an instrument for directing the ova to their proper location at the 

 period of extrusion. 



The generative system of the arachnida and Crustacea is very 

 simple, consisting in the male, of testes and vasa deferentia, and in 

 the female, of membranous ovaries with their excretory ducts. 

 These organs are double in each sex, and quite distinct from each 

 other. 



In the mollusca, the generative organs present some peculiarities; 

 there is but one testicle in the male, and one ovary in the female, 

 each placed on the right side of the neck. The penis is of huge 

 dimensions in the gasteropoda, while in the cephalopoda it is quite 

 rudimentary; but, by way of compensation, the vas deferens is 

 large, convoluted, and muscular. 



When two snails amorously disposed, meet, as Professor Jones, 

 of London, lucidly observes, they begin their blandishments by 

 rubbing the surfaces of their bodies together; after some hours 

 the generative orifice on the side of the neck is seen to dilate, and 

 to display within its cavity three apertures, one from the penis, 

 another from the female organs, and the third from the sac which 

 contains a calcareous quadrangular spike, called the dart; the use 

 of which seems to be to excite to love its sluggish, sleepy, apathetic 

 associate, by pricking the surface of its body; at length his dart is 

 broken, and he becomes in turn the object of a similar attack ; both 

 the reptile cupids having thus exhausted their quivers, and received, 

 each, the love inspiring wound, the other two orifices now dilate, 

 from one the Ions: whip-like penis protrudes, and is received by the 

 vaginal orifice of the other; these phenomena being reciprocal, they 

 mutually embrace and impregnate each other. 



