Phylogeny of Animals 537 



and in the process successive migrations of evolving families 

 or genera steadily took place seaward, there to originate types 

 many of which became greatly calcified. 



Thereafter specializing condensation toward the decapod 

 series, and degrading condensation toward the sedentary and 

 the parasitic groups took place, in part in fresh water, but 

 more largely in the sea, that constitute great side lines of steady 

 evolutionary change, but which have failed to originate forms 

 higher than themselves. 



We venture to make the above statements with full cog- 

 nizance of two important positions reached during the past 

 quarter century. The first of these is that so admirably syn- 

 opsized by Korschelt-Heider, in which the view is advanced 

 that the Crustacea have developed from an annelidan ancestry 

 {112, II: \m). The second, advanced by Gaskell {176) and 

 much more elaborately by Patten {178), is that the fishes 

 and still higher vertebrates started from a crustacean basis. 

 Both of these positions seem to the writer alike strained and 

 morphologically unnecessary. 



In the scope of this work it is impossible to do more than 

 indicate that the three essentially land divisions of arthropods, 

 namely the Myriapoda, the Arachnida, and the Insecta, seem 

 all to have started from primitive entomostracan ancestry, 

 and in assuming a terrestrial life have gradually adapted them- 

 selves to the action of environal agents by reactions of varied 

 and in many cases increasingly perfected kind. 



All palseontological evidence tends to prove that the more 

 primitive divisions of the Crustacea must have been frequent 

 in the fresh waters and seas of later archsean time, for the 

 abundant remains of Ostracoda and Trilobita in oldest Cam- 

 brian rocks, and of other Entomostraca in silurian to carboni- 

 ferous rocks, often formed too in fresh water, could only have 

 resulted by descent from greatly older ancestors. But the 

 soft bodies or frail shells of many archa?an organisms militated 

 against preservation, while the quantity of oily compounds 

 that these contained, combined with the baking by volcanic 

 agency that was then frequent, would conspire to disintegrate 

 their remains. 



