S^i ART. 11. S. HAÏTA. 



there is detected, in a «mall extent of the hind region, a process 

 which resembles concrescence. But that seems to me to be 

 of a significance difterent from the process which embryologists 

 are wont to call by the name just mentioned ; the process observed 

 by me is probably identical with that which was pointed out in 

 the Amphibia by Eycleshymer.^^ 



3. I have stated that the macromeric hemisphere has an 

 activity of its own. This is an important factor in bringing 

 about the gastrulation in Petromyzon, That such is the case in 

 the Petromyzon ovum which contains much larger quantity of yolk 

 than the frog's ovum and that there is no yolk-plug in the 

 former are very striking facts. I can find no other way of 

 explaining this peculiarity than by assuming the frog's ovum to 

 be secondarily holoblastic as was maintained by Professor Mitsu- 

 kuri seven years ago.'-' I intend to deal with this question more 

 fully at another place. 



I wish to express my deepest thanks to Professor Mitsukuri 

 for his kindness in looking through the manuscript. 



Nov. 26, 190o. 



1) A. C. Eyclesliyiner : Tlie Formation of tlie Embryo of Necturus, witli Kemarks 

 on the Theory of Concrescence. Anat. Anz., Bd. XXI, 1902. 



2) K. Mitsnkuri : On the Fate of the Blastopore, the Relations of the Primitive 

 Streak, and the Formation of the Posterior End of the Embryo in Chelonia, together with 

 Remarks on the Nature of Meloblastic Ova in Vertebrates. Journ. Coll. Sc, Imp. Univ., 

 Tokyo, vol. X, 1896. 



