TO THE EMBRYOLOGY OF AMPHIBTA. 85 



of development in the naturally growing eggs. Thus, in the 

 above experiments the facts observed in Group I., Nos. 5 and 10; 

 Group IL, Nos. 1 and 10; and Groups III., and IV., No. 10 

 appear to speak strongly for Morgan's views, while the eggs, 

 No. 5 of Groups II., IIL, and IV., would become data favorable 

 to the opinions of Pflüger, Roux and others. Again a third 

 group (Group I., Nos. 3, G, and 8 ; Group II., Nos. G and 8 ; 

 Group III., Nos. 3 and G ; Group IV., Nos. 2, 3, 6, and 7) would 

 go to support Schulze and others who maintain the older views. 

 The truth is : none of these shows the normal eousre, and we 

 must look deeper for a general law that would include and explain 

 all these cases. 



12). For my own part, I am inclined to accept the isoiro- 

 pism of the frog's egg. According to this view there is no fixed 

 law that the embryonic body in Amphibia must be formed in one 

 particular region and in no other part of the egg-surface. When- 

 ever there is sufficient reason, the embryo can be formed at 

 any part of the egg-surface. It is true that in the ordinary 

 course of the normal development the embryonic body, as already 

 mentioned, appears along the meridian of the blastopore within 

 the equatorial zone. This general rule has been produced by a 

 long course of inheritance and is no doubt most beneficial to 

 the growth of the egg. But whenever there occurs any great 

 obstacle so that the egg can not grow in the usual way, it does 

 not stop its growth at all, but seems always trying to overcome 

 the obstacle in one way or another, and to continue its develop- 

 ment. In this manner there result various kinds of abnormalities, 

 natural or artificial. If it were true that the embryonic body could 

 be formed only at one particular region and in one particular 

 manner, there ought not to be normal embryos produced in 



