FATE OF THE BLASTOPORE IN RANA TEMPORARIA. 49 
Note on the Fate of the Blastopore in Rana 
temporaria. 
By 
Harold Sidebotlinm, M.R.C.S. 
With Plate V. 
In the description given in Balfour’s ‘ Comparative Em- 
bryology ’ of the development of the Amphibia, that portion 
of it which specially relates to the anourous Amphibia is 
mainly founded on the researches of Gotte on Bombinator. It 
is there stated that 1 “ at first the mesenteron freely communi- 
cates with the exterior by the opening of the blastopore. The 
lips of the blastopore gradually approximate, and form a pas- 
sage, on the dorsal side of which the neural tube opens .... 
The external opening of this passage finally becomes oblite- 
rated, and the passage itself is left as a narrow diverticulum, 
leading from the hind end of the mesenteron into the neural 
canal. It forms the post-anal gut and gradually narrows, and 
finally atrophies. At its front border, on the ventral side, 
there may be seen a slight ventrallv directed diverticulum of 
the alimentary tract, which first becomes visible at a somewhat 
earlier stage. This diverticulum becomes longer and meets an 
invagination of the skin, which arises in Rana temporaria 
at a somewhat earlier period than represented by Gotte for 
Bombinator. This epiblastic invagination is the proctodseum, 
and an anal perforation eventually appears at its upper 
extremity.” 
1 Balfour, * Comp. Embryology,’ 2nd edit., vol. ii, p. 130. 
VOL. XXIX, PART ]. NEW SER. 
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