ORGANS OF GENERATION. 



413 



male, and measuring in some cases upwards 

 of six feet. These tubes, after becoming con- 

 siderably increased in size so as to form a 

 kind of receptacle for the ova which they 

 generate, unite prior to their termination in 

 the vulva, the aperture of which is found upon 

 the ventral surface of the body at about one 

 third of its length from the anterior extremity. 

 In Strongylus the ovarian tube is single, and 

 its orifice nearer to the mouth. In many 

 species, as Filaria, the young are produced 

 alive, the ova being hatched in the oviduct, 

 a sufficient proof of internal impregnation 

 having been accomplished. 



The Myriapoda, in every part of their struc- 

 ture, form the transition from the Annelida to 

 the articulated classes properly so called. They 

 are divided by entomologists into two classes, 

 the lulidtf or Chilog7iatha, and the Sculopen- 

 drldiE or Chilopoda, a division strictly in con- 

 formity with their internal structure; the former 

 ii fact represent the Annelida; like the Abran- 

 chiate division of that class, they breathe by 

 air-sacs, communicating with spiracles seen 

 upon the exterior of their bodies. The Scolo- 

 pendrae, on the contrary, respire by tracheae, 

 which permeate their viscera, as in the insect 

 classes. In the generative system of these 

 creatures a similar relationship is evident. In 

 luluSf the generative system occupies the ante- 

 rior segments of the body, the sexual apertures 

 being found upon the rings near the cephalic 

 extremity, whilst in Scolopendra they are placed, 

 as in insects, near the anal orifice. As regards 

 the internal sexual organs of lulus, but little is 

 known conclusively, and our own researches 

 upon this point have not been sufficiently satis- 

 factory to enable us to speak positively con- 

 cerning them, although the result leads us to 

 suspect that in these creatures not only are the 

 sexual parts analogous to those of the Anne- 

 lida, but that, as in many of that class, the ova 

 are retained in cellular interstices surrounding 

 the intestinal canal for some time prior to their 

 expulsion. 



In the Scolopendra the generative organs are 

 more easily distinguishable, and much resem- 

 ble those of insects ; they are, however, exceed- 

 ingly curious. Inj^f. 201 we have represented 

 the male apparatus of the Scolopendra mnrsi- 

 tans. The testes (o, a, a) are seven in number, 

 and closely packed in parallel lines; each testis 

 is composed of two parts, precisely similar to 

 each other, which are seen separate at b ; from 

 each extremity of the fusiform testis arises a 

 narrow duct, so that there are fourteen pairs of 

 ducts arising from the fourteen secreting organs. 

 Each of the testicular bodies is hollow inter- 

 nally. The ducts ultimately end in a common 

 tube (c), which soon becomes enlarged and 

 tortuous, terminating by a simple aperture near 

 the anus. Just prior to its termination, the en- 

 larged canal receives five accessory glands, four 

 of which (rf, rf, d, d) are intimately united, until 

 unravelled, as seen in the figure, while the fifth 

 (e} is a simple caecum of considerable length. 



The ovarian system of the female Scolopen- 

 dra is a single tube, apparently without secon- 

 dary ramifications. 



Male generative organs of the Scolopendra motsttans. 



Insects. In the numerous and diversified 

 tribes of the insect world a great uniformity is 

 observable in the general arrangement of the 

 generative apparatus. The sexes are invariably 

 separate, but while the internal organs are con- 

 stantly double and symmetrically disposed on 

 both sides of the mesial plane, the external 

 parts which are subservient to copulation are 

 removed to the posterior extremity of the body, 

 and are single. Throughout the whole class 

 the sexual system only arrives at that state of 

 perfection which is compatible with reproduc- 

 tion in the perfect or imago state of the animal, 

 although it may be detected in a rudimentary 

 form even in the larva, being gradually more 

 and more perfected during the developement 

 of the pupa. The business of procreation in 

 insects thus exclusively belonging to the per- 

 fectly formed creature, is accomplished only at 

 the termination of their existence, and the whole 

 tribe is remarkable from this circumstance. 



The internal generative organs in male in- 

 sects are described as consisting of three por- 

 tions, the testes with their rasa deferentia, the 

 vesiculae seminales, and the canalis excretorius. 

 The testes, or, in other words, those portions of 

 the apparatus which are supposed to furnish 

 the essential part of the fecundating fluid, like 

 the rest of the glandular system, consist of coeca 

 or utricles floating loosely in the abdominal 



