^'^ THE NEW EVOLUTION ^|^ 



we see them now and as they are represented in the 

 early fossils. 



The principle of recombination of characters in the 

 echinoderms as a whole, this recombination taking 

 place at very early embryological stages, seems ade- 

 quately to explain the sharp distinctions or very 

 broad mutations between the starfishes, brittle-stars, 

 sea-urchins, sea-cucumbers, and the crinoids and 

 their allies. 



In exactly the same way we may explain the sharp 

 distinctions between the gastropods, bivalves, scaph- 

 opods, cuttle-fish and other types among the mol- 

 lusks, and between the crustaceans, spiders, insects, 

 centipedes and other forms in the arthropods. 



Coming down to finer divisions, divergence in 

 relatively late embryonic stages would serve to ex- 

 plain the curious isolation of the skippers (Hesperioi- 

 dea) in the butterflies, and divergence in still later 

 embryonic life the sharp difference between the mega- 

 thymids and the other skippers. 



If the conclusion be justified that each phylum or 

 major group of animals represents the natural end 

 product of a special type of cell division, and that 

 all these special developmental lines leading from the 

 single cell to the different phyla appeared concur- 

 rently, resulting in the simultaneous formation of 

 some representative or other in all the major groups, 

 there should be further indications pointing in the 

 same direction. 



We have traced a hypothetical course of develop- 

 ment from the single cell to each of the various major 



[i02.] 



