14 ART. 11. S. HATTA. 



which the process goes on : every part of it is pronounced on the 

 external surface of the ovum. 



The previous authors give no account at all of the groove 

 just dealt witli. Max Schnitze only touches on it^^ ; however, 

 he ascribes to it, as above referred to, quite another meaning, 

 regarding it as the earliest indication of the blastopore. Prof. 

 Ch. Ishikaw^a discovered, independently from myself, the groove 

 in the Japanese Giant Salamander {Blegalohatrachus maximus), 

 of which an account of the early development was published 

 last summer."^ 



I will finally give a brief explanation of the changes 

 of the conical eminence which has been touched upon inci- 

 dentally. The conical eminence is at first brought about by 

 the commencing invagination of the opaque hemisphere, and in 

 the course of the 2:)rocess, it is extended and flattened into the 

 embryonic shield which is anteriorly and laterally bounded by the 

 boundary groove {Figs. 5a-8b). The embryonic shield comes 

 later to be produced in front into a conical knob from the upper 

 end of the ovum, when the translucent swelling containing a 

 small remnant of the segmentation cavity has been driven into 

 the ventral aspect {Figs. 9a and 9ô). When this swelling at 

 last disappears from the ovum and the ovum assumes a pear-shape, 

 a prominent elevation of an oval outline becomes obvious on the 

 dorsal surface of it ; it is rounded and broad in the anterior part 

 and is gradually narrowed towards the blastopore to become lost in 

 the neighbourhood of the lateral blastoporic lips {Fig. 10, m.p.). 

 This elevation is doubtless the medullary plate which answers 



1) loc. cit. p. 13. ^ ♦ 



2) Ch. Iwliikawa: Gastrulation of the Japanese Giant Salamander [Mcgalohatrachus 

 maiiiiiui). Zoul. Magaz., Vol. XVII, 1905. 



