DEVELOPMENT OF A XOX-AQUATIC TADPOLE. 261 



5. Hewitt refers Anhydroplirync^ which has a toothed upper 

 jaw, to the RanidcB, and in some respects it resembles the genus 

 Cacosternum which is also toothed, and perhaps should be 

 regarded as a Eanid, although it is usually grouped in the 

 EngtjstoinatidcB in which the upper jaw is tyi^ically toothless. 

 In both genera there is a firmisternous pectoral girdle in which 

 there is an expanded coracoid but no clavicle or precoracoid. In 

 the embryo of AnliydropJiryne there is a well-marked precoracoid 

 cartilage, but probably such is also the case in the tadpole of 

 CacosterniDn . 



6. In association with the shortening of the vertebral column 

 in the Anura there appears to be a general tendency for the 

 ilia to extend anteriorly beyond the sacral vertebra. This condi- 

 tion is well-marked in the tadpole of Anhydrophrync where the 

 ends of the ilia extend as far forwards as the level of the 

 diapophyses of the vertebra in front. 



7. The sacral diapophyses of adult Anhydrophrync are 

 dilated distalh% but are not relatively so broad as in 

 (.'acosterniiDi. In the embryo of Ayiliydrophryne the sacral 

 diapophyses are large and almost cylindrical and Eanid in 

 character, but before any conclusion can be drawn from this 

 fact it would be necessary to know the condition of these struc- 

 tures in the tadpoles of other genera. The evidence of the 

 present investigation certainly supports the view that the 

 characters of tadpoles in general are very largely adaptive, and 

 consequently great caution is necessary in drawing phjdogenetic 

 conclusions. 



EXPLANATION OF PLATES. 



Plate II. 



Fig. 1. — Segmenting egg of Anhydirophryne rattrayi. View from above 

 showing four incompletely separated blastomeres. x 10. 



Fig. la. — Vertical section of segmenting egg showing undivided yolk-mass 

 below, with a peripheral layer of protoplasm continuous with the 

 blastomeres above, which contain numerous half-sized yolk-globules. 

 X 60. 



Fig. lb. — Upper and lower portions of a vertical section at a stage .similar 

 to that of fig. la, showing cleft-cavity and grooves of incompletely 

 separated blastomeres ; also, coarsely granular reticulum of protoplasm 

 between yolk-globules, and superficial layer of protoplasm around yolk- 

 mass with smaller yolk-globules. X 300. 



Fig. 2. — Ovum with shield-shaped blastoderm. X 10. 



Fig. 2a. — Vertical section in long-axis of blastoderm. Blastoderm consists 

 of a thick, richly nucleated syncytial layer which is growing along the 

 margins and is continuous with the peripheral layer of protoplasm 

 surrounding the undivided yolk-mass below. It would appear that 

 nuclei (n) migrate from the blastodermal syncytium into this superficial 

 layer, and also into the neighbouring yolk (n.y.). In the lower quadrant 

 it is supposed that the yolk-globules have been removed in order to 

 display the protoplasmic reticulum. x 30. 



Fig. 2b. — Upper and lower portions of a vertical section (cf. fig. 2a) 

 showing syncytial blastoderm with scattered nuclei, vacuole-spaces and 

 yolk-globules of small size. In lower portion a nucleus is seen in the 

 superficial protoplasm and also one in the periphery of the volk-mass. 

 X 300. 



