324 J. S. BUDGETT. 



constricted off, and the back wall of the lens has begun to 

 thicken and fill up the hollow of the lens {I.). 



Section XVI is a sagittal section through the pineal eye of 

 an embryo about two days before hatching. It shows the 

 pineal stalk, still allowing free communication between the 

 pineal body and the brain-cavity ; this passage is now dis- 

 tinctly ciliated {cil. st.). Blood-sinuses are seen in front and 

 behind. 



Section XVII is a transverse section of an embryo just 

 before hatching. It passes through the root of the first ex- 

 ternal gill {Ext. G.), and shows the developing first and second 

 internal gills {Int. G.). 



From this and similar sections there certainly does not seem 

 to me to be any very marked difference in the nature of the 

 external and internal gills. 



As regards the development of the Pronephros and its 

 duct, my sections indicate that there is considerable variation. 

 Though by the time the external gills are developed there are 

 invariably three nephrostomes, as in Rana, the first and third 

 being lateral, the second dorsal, yet previously to this stage 

 I find often only two nephrostomes, and in some instances two 

 on one side with three on the other, and in one case but one. 

 This seems to me to indicate that the pronephric tubules do 

 not arise in the way usually described for Rana, namely, by 

 the primitive pronephric groove becoming a closed tube and 

 remaining in open communication with the coelom at three 

 points, but rather as a solid rod of mesoderm (Section VII), 

 which later becomes hollow and acquires perforations into the 

 coelom, at first one, later three points — the nephrostomes. 



In comparing the development of Phyllomedusa hypo- 

 chondrialis with that of Rana, Bombinator, Pelobates, and 

 other Batrachians with free-swimming larvae, the first thing 

 that strikes one as regards external characters is that, through- 

 out, this embryo maintains a greater similarity to ichthyic 

 forms, especially Ganoids, on the one hand, and to the Uro- 

 dela on the other, than do the free-swimming larvse of other 

 Batrachians, 



