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COMPARATIVE ANATOMY 



ovid.r. . 



f.k. .- 



test.r. - 



ovid.l. 



ovid.r JJL/1 



cvid.l. 



Fig. 463. 



Hermaphrodite Frog, f.k., fat-bodies ; n.Z. 

 and n.r., left and right mesonephroi ; ovid.l. 

 and ovid.r., left and right oviducts ; teat.l. and 

 test.r., left and right testes. (After Mitro- 

 phanoff.) 



While internal fertilization 

 takes place in most of the higher 

 forms of animals, there are many 

 vertebrates such as the cyclostomes, 

 most fishes with the exception of the 

 elasmobranchs, and many amphibia 

 in which fertilization does not take 

 place until after the eggs have 

 passed from the body of the female. 

 The organs by which sperm is 

 passed to the female are formed in 

 many ways and are not considered 

 homologous in the different forms. 

 As we already know from our 

 study of the earthworm, there are 

 animals possessing both ovaries and 

 testes. Such animals are commonly 

 termed hermaphrodites. True her- 

 maphrodites must have both ovaries 

 and testes functional. (Fig 463.) 

 It is interesting to note that while there are occasional hermaphro- 

 dites among the lampreys, this is a rather common occurrence in the 

 myxinoids. In these the cephalic end of the gonad is male, and the caudal 

 end female. However, usually one or the other of these functions, so 

 that the animal is either predominantly male or female. Hermaphroditism 

 has been found among the frogs, while in toads there is often a "pidder's 

 organ" lying directly in front of the gonads of the male but containing 

 immature ova. (Fig. 457.) Cases of hermaphroditism, although possi- 

 ble, are seldom found in mammals, the so-called cases being merely 

 arrested growth in the male, preventing the two portions of the scrotum 

 from joining in the mid-line, or an hypertrophy of the clitoris in the 

 female. 



ADRENAL ORGANS. 



Closely associated with the nephridial structures lie two. small duct- 

 less glands, one connected with each renal organ in the higher forms. In 

 the lower vertebrates each one of these is in turn composed of two 

 structures. In the amphibia and amniotes one portion, called the 

 suprarenal, forms the medulla while the interrenal forms the cortex of 

 the mammalian adrenals. (Fig 351.) The suprarenal portion is always 

 connected with the sympathetic nerve ganglia, some of the cells always 

 retaining their nervous character. Other cells, because they stain brown 

 or yellow with chromic salts are called chromaphile or phaeochrome cells. 

 (Fig. 464.) These are usually quite closely related to blood vessels. 



