354 COMPARATIVE MORPHOLOGY OF VERTEBRATES 



occur. These are formed in several ways and are not homologous 

 throughout. Hence they will be considered here under the separate 

 groups. 



Hermaphroditism 



Individuals of either sex which have assumed some of the external 

 or secondary sexual characters of the other sex are sometimes spoken 

 of as hermaphrodites, especially in the case of mammals if the copu- 

 latory organs be concerned. This is not true hermaphroditism, 

 which consists in having both ovarian and testicular organs or tissues 

 in the same individual and as a consequence the ability to produce 

 both eggs and spermatozoa. There may be both kinds of tissue in 

 the different parts of the same gonad, or the two may be intermingled 

 (ovotestis) or the gonads of the two sides of the body may be of 

 different sexes. Both ovaries and testes may be functional at the 

 same time, or one may be functional at one time and the other at 

 another (proterandric hermaphroditism). 



Among the cyclostomes there are occasional specimens of lam- 

 preys which have been regarded as hermaphroditic, but in the 

 myxinoids this is the regular occurrence, the anterior end of the gonad 

 is female and the posterior male. One or the other of these is func- 

 tional, the animal being predominantly either male or female, and 

 some individuals are regarded as sterile. Nansen regards this as a 

 case of proterandric hermaphroditism. In the teleosts several species 

 of Serranus are regularly hermaphroditic as is Chrysophrys aurata, 

 while in several other species it is an occasional occurrence. Triton 

 tceniatus is the only urodele in which it is reported, but in the anura it 

 is most common. Thus it is frequent in the frogs and occasional in 

 other genera. In the toads (Bufo) there is frequently a 'Bidder's 

 organ' in front of the gonads which contains immature ova in the 

 male. Among the birds the phenomenon has been reported in the 

 chaffinch. (The assumption of male plumage by female birds at 

 the close of sexual life is not a case of hermaphroditism.) Among 

 the mammals the cases are extremely rare, but cases, apparently 

 well authenticated, have been reported in the goat, pig and man. 



I^M^- ADRENAL ORGANS 



Under this heading are included two sets of structures, interrenals 

 and suprarenals, of uncertain morphology and function. The names 

 are given in allusion to the fact that they are usually closely associated 



