ORGANS OF GENERATION. 



417 



both Bonnet and J urine observed that the fe- 

 male Aphides and Branchiopods that were 

 fertile without the usual intercourse of the 

 sexes were less fruitful than their mother, and 

 those of the last generation less so than the 

 first. 



Arachnida. In the Arachnida the gene- 

 rative system, both in the male and female, 

 is even more simple than that of insects. The 

 testes of the male are two in number, each 

 being an elongated membranous bag, closed at 

 one extremity, whilst the opposite is conti- 

 nuous with a slender and tortuous vas deferens, 

 the terminations of which are indicated ex- 

 ternally by two very small orifices distinguish- 

 able on the under surface of the abdomen near 

 its junction with the thorax. The apertures 

 through which the seminal fluid is discharged 

 are totally unprovided with any apparatus of 

 intromission or excitement; in lieu of which 

 many genera are provided with a singular sub- 

 stitute, or at least with an organ supposed by 

 some authors to be an exciting organ. This is 

 found at the extremity of the maxillary palpus, 

 but for a detailed account of its structure and 

 presumed functions the reader is referred to the 

 article ARACHNIDA. 



The female organs of the Araneidae are 

 equally devoid of complication. The ovaries 

 are simple membranous bags, which occupy 

 when distended a considerable portion of the 

 abdomen, and are found to contain ova ag- 

 gregated together in considerable numbers. 

 From each of these ovigerous sacs a short 

 canal leads to an aperture situated near the 

 base of the abdomen, through which, when 

 mature, the ova are discharged. The most re- 

 markable circumstance observable in this form 

 of the generative system is the complete sepa- 

 ration which exists between the sexual organs 

 of the two sides of the body, which, both in 

 the male and female, not only do not com- 

 municate internally, but open upon the exterior 

 by distinct apertures; the insulation is, in fact, 

 so perfect that in some cases the eggs gene- 

 rated in the two ovaria are laid at distinct and 

 distant periods. According to Audebert some 

 spiders are rendered fertile for several years by 

 one intercourse with the male. 



In the Scorpions the male generative ap- 

 paratus consists of a testis composed of nu- 

 merous tubes united together, so as to form a 

 series of loops, the secretion of which is dis- 

 charged externally by a double penis resembling 

 that of some reptiles, which is protruded 

 through a valvular aperture seen upon the 

 ventral surface of the thorax. 



The female organs of the Scorpion, like 

 those of the male, are composed of loops of 

 tubes, uniting together at different points, and 

 when distended with ova resembling a neck- 

 lace of beads : they open by two canals, (vol. i. 

 Jig. 84, c, p. 205), at the same point which the 

 sexual aperture of the male has been seen to oc- 

 cupy, each having a small crecum or succentu- 

 riate gland appended near its termination. The 

 eggs of Scorpions are hatched in the oviducts, 

 and the progress of the developement of the 

 embryo maybe easily distinguished through the 



transparent coats of the ovum ? resembling most 

 accurately that observed by lierold in the evo- 

 lution of the young spiders, figures of which 

 are given elsewhere.* 



Crustacea. As in the Arachnida, the gene- 

 rative system of Crustaceans is for the most 

 part double, the parts belonging to the two 

 sides of the body being generally completely 

 distinct from each other, not only internally 

 but at their termination. In the higher orders 

 the testes of the male and the ovaries of the 

 other sex are found to be situated in the dorsal 

 region of the thorax ; in both cases these 

 organs appear at first sight to be of a dense 

 glandular structure, but, on examination, are 

 found to be essentially composed of tubular 

 convolutions. In both the male and the fe- 

 male, the excretory canals are simple tubes, 

 which, after some convolutions, terminate in the 

 male by prominent apertures, found upon the 

 coxal portion of the fifth or posterior pair of 

 true legs, and in the female by similar open- 

 ings at the base of the third pair. 



As in Insects, the female organs have in 

 many genera a sacculated appendage, or copu- 

 latory pouch as it is termed, which is, in fact, 

 analogous in function to the spermotheca of 

 insects, serving as a reservoir in which the 

 male semen is detained for the purpose of im- 

 pregnating the eggs as they successively escape 

 from the body. After their exclusion from the 

 oviduct the eggs of Crustaceans are generally 

 carried about by the female. In the Decapoda 

 they are appended by a glutinous material to 

 the false feet situated under the tail. In the 

 Isopodn and others they are retained in recep- 

 tacles formed by scales placed under the ab- 

 domen, whilst in the Entoraostracous forms, 

 as well as in many Epizoa approximating the 

 Crustacea in structure, a remarkable provision 

 is made for perfecting the eggs external to the 

 bodies of these minute creatures, the females 

 being provided with one or two membranous 

 sacs appended to the posterior part of the 

 abdomen, into which the oviducts open, and in 

 which the ova are retained until they arrive at 

 maturity. 



Mollusca. Several of the more perfectly 

 organised Mollusca come likewise under this 

 division of our subject. Such are the Pectini- 

 branchiate Gasteropoda, in which the structure 

 of the generative apparatus is sufficiently sim- 

 ple. In the male a large testis, composed of 

 racemose follicles, shares with the liver the 

 convolutions of the shell : from this the seminal 

 secretion passes by a long and tortuous vas 

 deferens to the extremity of the penis, which 

 is in these creatures an extensile and veiy 

 muscular organ, situated on the right side of 

 the neck, and not unfrequently of enormous 

 size when compared with the bulk of the 

 animal. 



The ovarium in the female Pectinibranchiate 

 Gasteropods corresponds in position with the 

 male testis; the oviduct arising from it is 

 capacious, glandular, and convoluted, serving 

 in some genera, as in Turbo, as a receptacle 



* Vide Article ARACHNIDA. 



