258 development of a xox-aquatic tadpole. 



The Limbs. 



The hind-limbs api:»ear as buds extremely early in develop- 

 ment and arise as soon as the tail begins to be formed (PI. II, 

 figs. 3, 4). The fore-limbs appear a little later as slight knobs 

 between the head and yolk-mass. At first these knobs are entirely 

 exposed. Very soon, however, a fold of epidermis begins to grow 

 over them from behind, and before long each of the fore-limbs is 

 completely enclosed by a separate fold. Curiously enough, these 

 folds are not back-groM^ths of the epidermis from the hyoid region. 

 The folds arise behind the head on each side of the middle line. 

 They grow obliquely forwards and downwards ; they cover the fore- 

 limb buds and fuse on to the epidermis in front of and below the 

 buds. It is not possible to regard these folds as non-homologous 

 with a true opercular fold, but the fine of origin of the fold has 

 been shifted away from its typical position. In the development 

 of Hylodes vutrfiniccusis Miss Sampson described a very closely 

 similar condition. 



The first two gill-slit pouches of the pharynx come into 

 contact with the epidermal lining of the atrial cavity, but no trace 

 of perforation appears. The opercular or atrial chambers of the 

 two sides remain widely separate and quite distinct from each 

 other. Perforation of the operculum by the fore-limbs occurs 

 late in the metamorphosis. 



Larval Sucker. 



There is no sub-oral sucker at any period, and I could detect 

 no trace of even a rudiment of the structure. 



Tail. 



The tail is long and is provided with mid-dorsal and ventral 

 membranes. It is moderately vascular, but not appreciably more 

 so than in an aquatic tadpole. Thus the terrestrial mode of life 

 has not had any marked modifying influence on the tail. In 

 Hylodes ruartinicensis, on the other hand, the tail is short and 

 flattened, and according to Miss Sampson it is very vascular and 

 is used for aerial respiration. 



Skeletox. 



The sacral diapophyses are distally dilated in the adult, while 

 in the minute frog with a short tail the cartilaginous diapophyses 

 are thick but more or less cylindrical, and they exhibit no appre- 

 ciable terminal dilatation. The ilium cartilages are ventral to the 

 sacral diapophyses, and their free ends extend considerably 

 beyond the sacrum and reach the level of the small diapophyses 

 of the vertebra in front. Mr. Hewitt informs me that such a 

 forward extension of the ilia is not obvious in the adult. I am 

 not aware whether a similar condition occurs in developing Rana; 

 but judging from certain good drawings of adult anuran skeletons 

 in Peters' and Boulenger's publications there is a distinct 

 tendency for the ilium to extend somewhat considerably beyond 



