URIXOGENITAL ORGANS 



365 



phores, which pass into a large vesicula seininalis at the base of 

 the vas deferens ; the Miillerian ducts are complete in the male, 

 though small. 



Hernutplinidittsm occurs amongst Fishes. InMyxiiie the posterior part of 

 the gonad usually first gives rise to spermatozoa, and subsequently the anterior 

 part til ova, so that self-fertilisation is prevented. Serranus and Chryso- 

 phrys, again, are hermaphrodite, and hermaphroditism has been occasionally 

 observed in various other Fishes {e.g., Gadus morrhua. Scomber scomber, 

 Clupea, Harengus). 



Amphibia. — The paired and symmetrical gonads of Amphibians 

 are situated in about the middle of the coelome ; their 

 form is usually modified by the shape of the body. Thus in the 

 Gymnophiona the ovary has the form of a long and narrow band, 

 while the testis is made up of a long chain of small bodies united 

 together by a collecting duct (Fig. 291). Each individual portion 



-IIS 



Fig. 291.— Diagram of a Portion" of the M.ale Generative Apparatus of 



the gvmnophioxa. 



Ho, Ho, testis ; Sg, collecting duct of testis ; K, K, testicular capsules ; Q, <,> 

 transverse canals connecting the collecting duct ^^•ith the longituduial canal 

 (L L) ■ (>' V', second series of transverse canals ; il, M, JNIalpighian 

 capsules ; X -V, kidney ; ST, nephrostome ; S, convoluted portion of urinary 

 tubule ; HS, urinogenital duct. 



of the testis of Ctecilians is made up of a double row of rounded 

 capsules in which the sperm is formed, and from which it is passed 

 into a collecting duct, which perforates each portion of the organ. 

 A transverse canal is given off from the free portion of the collect- 

 ino- duct lying between every pair of testis lobes ; this passes to- 



