340 THE ANATOMY OF INVERTEBRATED ANIMALS. 



single, and tubular in form. It lies above the alimentary 

 canal in the latter, between the alimentary canal and the ner- 

 vous system in the former. The double vaginae open on, or 

 close behind, the bases of the second pair of legs in the Chi- 

 lognatha ; at the posteri jr end of the body, beneath the anus, 

 in the Chilopoda. Two spermathecae and colleterial glands 

 are very generally present. 



The testes in the Chilognatha are tubular glands, which 

 occupy the same position as the ovary, and open in the same 

 region. They have lateral caeca, and are connected by trans- 

 verse ducts. Two copulatory organs, or penes, are developed 

 on the sternal face of the sixth segment which follows the 

 head, or are connected with the bases of the seventh pair of 

 legs. 



In the Chilopoda there is a good deal of variation in the 

 structure of the testis. Thus, in Lithobius^ the testis is a 

 single filiform tube, connected at the hinder end with two 

 deferent ducts which embrace the rectum. A large caecum, 

 apparently a vesicula seminalis, opens into each deferent duct. 

 But, in most Chilopods, the testes are fusiform acini, united 

 by delicate ducts with a median vas deferens. Two, or four, 

 pairs of accessory glands are connected with the opening of 

 the male apparatus. 



The spermatozoa are inclosed in spermatophores in Scolo- 

 pendra, Cryptops, and G-eophilus. 



The Chilognatha copulate. In Glomeris and Polyxenus 

 the genital apertures of the two sexes are brought together 

 during copulation ; but, in lulus, the penes of the male are 

 charged with the spermatic fluid before copulation takes place, 

 and it is by their agency that the female is impregnated. 



The Chilopoda have not been observed to copulate ; in- 

 deed, the female shows a tendency to destroy the males, as 

 among spiders. The male Geophilus spins webs like those 

 of spiders across the passages which he frequents, and depos- 

 its a spermatophore in the centre of each. 



Metschnikoff 3 has recently shown that, in the Chilognatha, 

 the process of yelk -division is complete, and confirms the obser- 

 vation of Newport (" Phil. Trans.," 1841), that the sternal face 

 of the blastoderm becomes sharply infolded down its centre, 

 in such a manner that the anterior and the posterior halves of 



1 Favre, " Anatomie des organes reproducteurs des Myriapodes." (" Annales 

 des Sciences Naturelles," 1855.) 



2 " Embryologie der doppelfussigen Myriapoden (Chilognatha)." (Zeit- 

 tchriftfur wise. Zoologie, 1874.) 



