4 Evolution and Distribution of Fishes 



mals as well as the land types. The marine environment 

 once reached, there were presented wide and continuous 

 fields of activity in migration, in feeding, in escape from 

 foes, in reproduction, and in rearing of the young. Varied 

 and changing environal stimuli steadily produced new and 

 varied forms that became increasingly adapted to marine 

 life, but seldom indeed showed capacity for readaptation 

 to freshwater, not to say land existence. 



In an address before the Academy of Natural Sciences 

 of Philadelphia in 19 12, the writer explained the appli- 

 cation of these principles to the leading groups of animals, 

 and an abstract of this address was published later by Dr. 

 A. W. Miller in his "Report on the Progress of Botany" 

 in "Proceedings of the 36th Annual Meeting, Pennsylvania 

 Pharmaceutical Association" (19 13). Such were his first 

 published statements regarding the origin of the important 

 groups of animals. In applying these principles to fishes 

 in the volume already quoted (p. 403) the writer expressed 

 himself as follows: "We would shortly sum up our con- 

 clusions by saying that the Cyclostomata were probably, as 

 they still are in part, of freshwater origin; that the Se- 

 lachii are and have been through long epochs nearly all 

 evolved as marine forms; that the Polypteridae are and 

 probably have been freshwater in habitat and history; that 

 the Dipneustei are similar to the last; that the Chondrostei 

 or spoonbill and sturgeon series agree with the two last 

 except that some of the sturgeons pass into the sea to feed 

 and return inland to spawn; that the Holostei are now 

 wholly freshwater; that of the thirteen suborders of the 

 Teleostei given by Boulenger, the first or Malacopterygii 

 are almost wholly freshwater, the third or Symbranchii are 

 mainly fresh — more rarely brackish water inhabitants, the 

 fourth or Apodes — that includes the eels — are rarely fresh- 

 water, usually marine and breeding there at considerable 

 depths, the fifth or Haplomi — that includes the common 

 pike — are largely freshwater though a fair number live 

 and even breed in the sea, and the remaining nine (Heter- 

 omi; Catosteomi, etc.) are almost wholly marine with rare- 

 ly freshwater inclusive genera. 



