TO ANNALS NEW YORK ACADEMY OF SCIENCES 



2. When these highland forms arrived in the same kind of environ- 

 ments, they often underwent identical evolution with that which was 

 taking place somewhere in the massive Amazon. 



3. The remainder of the similarity is due to marine immigrants. 

 The first part of this answer needs no further comment, but the second 



may appear to be absurd, at least to those who are not familiar either 

 with the South American fishes or with the environmental complexes in 

 which these fishes live. The view that the common highland genera of 

 fishes have often undergone identical evolution in similar environments, 

 even if these environments are well separated, is of the same general 

 nature as those given in the following publications. 



Bateson has shown in the case of Cardium edule of the Aral Sea that, 

 as the sea dried up, isolated basins were formed in which the salinity 

 was greatly increased, and under these conditions the cockles so separated 

 show similar variations under similar conditions. These shells of the 

 cockles in the higher to the lower terraces showed a progressive change 

 in regard to the following features : 



(a) Shells became much thinner. 



(&) Shells became highly colored. 



(c) Size of beaks became reduced. 



(d) Shells became smaller in size. 



(e) The grooves between the ribs on the outside appeared on the in- 



side of the shells as ridges with rectangular faces. 



(/) A great increase in length in proportion to the breadth of the 

 shells. 

 Are not the changes observed by Bateson as profound as required to make 

 ■Cichlasoma bimaculatum out of JEquidens portalegrensis, or vice versa? 

 In this case, the loss or gain of one spine makes a different genus and a 

 species. Thus it is with many other genera and species of fishes whose 

 •distribution must be explained by identical evolution in similar environ- 

 ments. 33 



MacDougal has obtained nearly all of the mutations observed by 

 de Vries in Holland from Oenothera lamarcTciana obtained in France, 

 England and Holland and planted in New York. He also obtained one 

 mutant, 0. albida, from 0. lamarcTciana Nantucket City. Even if 0. 

 lamarcTciana is a hybrid, it makes no difference, for at least part of the 

 common highland stock may also be hybrid. 



Tower has shown, both in nature and by experiments with humidity 

 and temperature on Leptinotarsa, that he could produce changes both in 



33 Some of the small differences may be purely somatic, which are not necessarily 

 Inherited. Experimental evidence is necessary to settle this point. 



