456 Evolution and Distribution of Fishes 



fishes, that were derived from more primitively freshwater 

 forms like Chimarrhichthys if we may judge from structur- 

 al resemblances, became slowly adapted by environal action 

 and proenvironal response to a deeper marine habitat. 

 Gradual increase in size of the eyes, increase in size of the 

 head as compared with body-size, lengthening of some of 

 the fin-rays, formation of accessory dermal outgrowths, 

 softening of the tissues, and frequent softening or thinness 

 of the bones, are a few of the structural changes usually 

 effected in the process. 



It will be observed that the writer has described a 

 gradual migration of plants and animals from the American 

 continent eastward to beyond Australia and New Zealand. 

 This is absolutely necessary' when we trace phylogenetically 

 the affinities and ancestral habitats of most of the plants 

 and animals that peopled the entire Southern continent. For 

 the great majority clearly indicate such a west-to-east mi- 

 grational trend. This would lead one to believe also that 

 in upbuilding of the southern continent, a wave of elevation 

 took place in like direction. And further it is not only 

 unnecessary to consider that all points of the southern con- 

 tinent were in geographic continuity at one time, the known 

 facts indicate that New Zealand, Norfolk Island, and the 

 Fijis, were connected with Australia as well as America 

 at one time and then separated; also that the connection 

 with S. and S. E. Africa was relatively a short one. 



But that a certain amount of migration in the reverse 

 or opposite direction occurred, is proved we believe by not 

 a few facts of organic distribution, notably by that of 

 plants. A few only can here be referred to. Thus the large 

 and ancient angiospermic family Proteaceae is pre-eminent- 

 ly Australian, and the most primitive genera like Bellen- 

 dina, Symphyonema, and Persoon'ia still inhabit the same 

 region. But a westward migration must early have started, 

 at a time when the southern continent was about its maxim- 

 al size, and this probably in Early or Mid-Eocene time. 

 So ancestors of the fairly evolved genera Mimetes, Nivenia 

 and Serruria reached S. Africa, and there they, with suc- 

 ceeding migrants or evolved genera from these three have 



