GENEEATIVE OEGANS OF VEETEBEATA. 611 



except those above mentioned, have the tubular form. The germinal 

 region is often limited to one portion of the tube, whence it extends 

 more or less considerably, according to the degree to which its 

 products are developed. The lateral efferent ducts of these genital 

 tubes (Fig. 347, tt), are united into a common duct, which opens by 

 the genital pore. In this arrangement the germ-gland is not 

 ordinarily represented by the whole apparatus, but by the germi- 

 nal region only, which projects on the inner wall of the tube, 

 and is often lobed or branched. The germinal region is probably 

 invested by the Mullerian duct, which is converted into a tubular 

 form, but this has still to be established by embryological observation. 

 In a number of Teleostei hermaphrodite arrangements have been 

 observed, a testicular as well as an ovarian tube being developed ; 

 this is best known in species of the genus Serranus. 



§ 452. 



In the Selachii the arrangement which obtains in the female 

 Ganoi'dei is retained and further developed. The germ-glands 

 are generally developed on a certain portion only of the genital 

 ridge, while the rest of the organ has its stroma increased in 

 thickness, and converted into a special tissue (epigonal organ). As 

 a rule, the ovaries are paired, and lie some way forward. In many 

 the left one is rudimentary (Mustelus, Galeus, Scyllium, Pristiurus, 

 Carcharias). The long oviducts, which are developed from the 

 Mullerian ducts, unite with their fused abdominal mouths to form a 

 wide infundibular opening; this is correlated with the great size 

 of the eggs which it has to take up. The hinder end of each ovi- 

 duct is differentiated into a portion which is distinguished by its 

 greater width, and often by its thicker walls ; this generally func- 

 tions as a uterus, and opens into the cloaca. In the Selachii, as well 

 as in the Chimasras, a glandular portion is differentiated close 

 to the abdominal end of the oviduct. The generative organs 

 of these two groups, and of the Dipnoi, agree in the most essential 

 points. 



In these divisions the male organs are generally represented by 

 small testes, the ducts of which are connected with the anterior 

 portion of the excretory organs, so that this portion of the primitive 

 kidney, with its efferent ducts, is adapted to the service of the 

 generative apparatus. After several coils the vas deferens passes 

 to the cloaca; in Chimasra it first unites with its fellow of the 

 opposite side ; it generally opens with the ureter into a sinus 

 urogenitalis, which opens by a papilliform process into the cloaca. 

 Part of the Mullerian duct remains connected with the infundibular 

 ostium, at the same point as that at which it is found in the female. 

 At the binder end also a portion remains connected with the cloaca, 

 in the males. The Mullerian duct in Chimasra is retained in the same 

 way. In the males of the Selachii and Chima3ra3 certain parts of the 

 posterior appendages are converted into copulatory organs (p. 487). 



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