334 



COMPARATIVE MORPHOLOGY OF VERTEBRATES. 



branchs excepted. The gonads are roughly correlated in form to the shape of the 

 body, being shortest in the anura, longest in the caecilians and urodeles. The 

 ovaries are saccular (a single long sac in urodeles, a number of short ones in anura) 

 and the eggs pass into the cavity and then break into the coelom. The oviducts 

 are Miillerian ducts with ostia far forward. In the adults 

 they are greatly coiled and are glandular, their walls se- 

 creting the gelatinous substance which envelops the eggs. 

 Usually the oviducts of the two sides open separately into 

 the cloaca, but the two unite behind in Bufo. 



The testes have both the longitudinal and the testicular 

 canals connecting the efferent ductules. In the gymno- 

 phiona (fig. 334) the testes resemble a string of beads, each 

 bead consisting of a number of seminiferous sacs, the 

 string being united by the testicular canal. The efferent 

 ducts pass through the mesonephros, sometimes utilizing 

 the nephridial tubules, sometimes pursuing a separate course, 

 the two conditions being found in different species of frog 

 (Rana) in Europe. Our species have not been studied in 

 this respect. 



The cloaca of the urodeles has a glandular lining and in 

 the females it contains tubules which act as reservoirs of 

 sperm. In the male the glands secrete a substance binding 

 the spermatozoa together In many urodeles fertilization 

 is internal, though there is no intermittent organ save the 

 somewhat protrusible cloacal opening. 



There are many interesting accessory reproductive rela- 

 tions among the amphibia. Thus the caecilians and Am- 

 phiuma lay their eggs in long strings in the soil and the 

 female incubates them. The male often takes charge of the 

 eggs. In Pipa each egg undergoes development in a pit in 

 the skin of the back of the female and in Nototrema and 

 Opisthodelphys (South America tree-toads) there is a large 

 pocket in the skin of the back, opening near the coccyx, 

 where the eggs are carried until partially (Nototrema) or 

 entirely developed. Salamandra maculosa and S. atra bring 

 forth living young, the former being born with gills, the latter 

 in the perfect condition. Oviposition usually occurs in the 

 spring in colder climates (in the autumn with Cryptobranchus 

 of America) and as the drain on the system is very consider- 

 able immediately after hibernation, the substance of the 

 fat body, which always is closely connected with the gonads, 

 is utilized at this time. 



SAUROPSIDA. The birds and reptiles agree in the broader features of the 

 amniote urogenital system as outlined in the general account above. There is a 

 general correlation between the shape of the body and that of the gonads, and often 

 there is a lack of symmetry between the organs of the two sides Thus in snakes 



FIG. 334. Male 

 urogenital organs of 

 Epicrium, after 

 Spengel. a, anus; b, 

 urinary bladder; d, 

 cloaca;/, fat bodies; 

 m, Mullerian ducts; 

 mg, glandular part 

 of same; t, testes; tl, 

 longitudinal testi- 

 cular canal; w, 

 Wolffian body. 



