I 3 2 HABITUDES AND ATTITUDES 



them and through the gill-clefts of the foster- 

 parent. Day observed the same incubation in 

 the allied genus Osteogeniosus, and Dr Gunther 

 and others had recorded them for South American 

 species of Arius. 1 



Over against the buccal incubation of fishes 

 we may place that of the Chilian toad - like 

 Batrachian, Rhinoderma datwini, which was 

 regarded as one of the most interesting finds 

 of the voyage of the Beagle, although it is not 

 mentioned in Darwin's " Naturalist's Voyage." 

 The male of this toad possesses a median gular 

 sac, representing an extension of the buccal 

 cavity, which opens by two apertures on the 

 floor of the mouth. At the breeding season it 

 becomes a large brood-pouch, lying freely in the 

 ventral lymph-sinus and reaching back to the 

 pubic region. Jiminez de la Espada, who first 

 brought this fact to light in 1872, found as many 

 as fifteen metamorphosing larvae in the brood- 

 pouch. Howes 2 dissected a male in 1888 which 

 contained eleven larvae ; unlike the eggs and fry 

 of Arius, these larvae were unequally advanced, 

 only five of them being still provided with a tail. 



Espada noted a shrinkage of the viscera as if 

 the foster-parent had ceased to feed during the 



1 In the Japan-British Exhibition (1910) specimens of a Nile fish, 

 Tilapia nilotica^ are exhibted by Mr C. L. Boulenger, showing 

 females carrying their eggs and fry in the mouth. The eggs are 

 small. 



2 G. B. Howes, " Notes on the Gular Brood-Pouch of Rhino- 

 derma dariuini" P. ZooL Soc. y London, 1888, pp. 231-237. 



