GENERATIVE ORGANS. 



317 



Finally, the so-called fat- bodies (corpora adiposa) must be mentioned : 

 these are present in all Amphibia in connection with the generative glands, 

 and are formed of adenoid substance, fat, and leucocytes, and contain numerous 

 blood-vessels. They are apparently formed by the degeneration of the anterior 

 part of the genital ridge, and " Bidder's organ " (see p. 316) in the Toad seems 

 to represent a part of the ridge which has not become degenerated so far. 

 The corpora adiposa probably have an important physiological (nutritive) 

 relation to the generative glands ; this gives an explanation of the fact that 

 Amphibians, after remaining for months, throughout their winter sleep, with- 

 out food, are able as soon as spring arrives to give rise to thousands of offspring. 

 The curious lymphoid organs of many Fishes and Eeptiles have probably a 

 similar function (comp. pp. 304 and 320, and Fig. 24n). 



FIG. 248. URINOGENITAL OKGANS OF A FEMALE liana esculcnta. 

 Ov, left ovary (that of the right side is removed) ; Od, oviduct ; Of, abdominal 

 aperture of oviduct ; Ut, the dilated posterior end of the oviduct ; P, opening of 

 latter into the cloaca ; N, kidneys ; S, S l , apertures of ureters into the cloaca, sur- 

 rounded by longitudinal folds (*), which are separated by a deep depression (t). 



Reptiles and Birds. In these, as in other animals, the form 

 of the gonads becomes modified by that of the body. Thus in 



yellow in colour, and consists of both yellow and white granules. They are coated 

 with a tough albumen in the oviduct, and this becomes drawn out at the poles into 

 chalazae, by means of which the eggs are connected together like the beads of a 

 necklace. The}' are laid in the earth, and the mother coils herself round them. 



