16 ART. 3. S. IKEDA : CONTRIBUTIONS 



Owing partly to the fact that I spent the first three weeks 

 or more of the 1 »reeding season (in 1899) in making tentative 

 experiments in methods, and partly to the faet that I was deter- 

 mined to observe only absolutely normal eggs, removing from the 

 mirror-snrfaee eggs that showed the least sign of abnormality, 

 the number of cases I have observed is not at all proportionate to 

 the large number of eggs which I have examined. Only thirteen 

 eggs (Eggs A-M), have been subjected to continuous observation, 

 and of these only three (Eggs C, H, and I) gave entirely satis- 

 factory results, while the remaining ten showed more or less 

 imperfection during the observation. 



During the spring of 1900, I subjected the eggs of two 

 other anurans found in Tokyo, (Ran a japonica and Bufo japo- 

 nica) to the same observations. The number of the eggs employed 

 by me three were of the former, and seven of the latter species. 

 Of these, those that gave sufficient results were respectively one 

 of the first, and two, of the second species. This small number 

 was owing partly to the brevity of the breeding season in these 

 species, as compared with Rhacophorus, and partly to the clouding 

 of the mirror, the amalgam appearing unable to stand prolonged 

 submergence in water. 



I may here add a few words of explanation in regard to 

 Figs. 20-50 which have been selected out of innumerable drawings 

 to illustrate this section. The heavy horizontal line under every 

 lateral, and some posterior views of the egg is the level of the 

 mirror surface and is to be referred to as the standard line. The 

 second thick horizontal line through the centre of the egg is 

 drawn parallel to the standard line in order to denote approxi- 

 mately the equator of the egg. The third line, vertical to the 

 standard line, passing through the egg-centre gives the vertical 



