No. .m(>] 



ALPHEUS HYATT 



205 



the Unionidae. Larval adaptations are most marked in 

 the youthful stages of some insects, as in caterpillars. In 

 most invertebrates, however, at least in postembryonic 

 stages, larval adaptations are uncommon and can usually 

 be eliminated as a factor in studying ontogenetic stages. 



The Hyatt principles have been used as a working 

 basis in the phylogenetic classification of three entire 

 classes of animals, the Brachiopoda and Trilobita by 

 Beecher 15 and the Echini by myself. 10 They have also 

 been used as a basis of partial classifications of Cepha- 

 lopoda by Hyatt himself, of Protozoa by Cushman, 17 of 

 Pelecypoda by Jackson, 18 of Gastropoda by Grabau, 19 

 and also to a certain extent in suggesting genetic relation- 

 ships in a number of other groups of animals and in 

 plants by various investigators. 



If I may be permitted to speak of my own studies. I 

 have recently completed a phylogenetic study of the 

 Echini, and throughout the work made use of the Hyatt 

 principles. In this use there was no occasion to qualify 

 a single one. To work out principles largely on one 

 group (the Cephalopoda) as did Hyatt, and then to have 

 his followers apply these principles successfully to many 

 widely separate groups, and even to seek and ascertain 

 facts on the basis of the implied principles, is strong evi- 

 dence that he got at fundamental truths. 



At present the phylogeny of invertebrates is little 

 studied, palaeontologists are largely occupied with ques- 

 tions of stratigraphy, and zoologists occupy themselves 

 with other lines of work. In future, as phylogenetic work 

 is prosecuted, I believe that Hyatt will be looked on as 

 the master mind who pointed out the methods by which 

 to ascertain the true phylogenetic relations of inverte- 

 brate organic forms. 



15 C. E. Beecher, "Studies in Evolution." New York, 1901. 



"B. T. Jackson, "Phylogeny of the Echini," Mem. Boston Soc. Nat. 

 Hist., Vol. 7, 1912. 



1T J. A. Cushman, "Developmental Stages in the Lagenida?," Amer. 

 Naturalist, Vol 39, 1905. 



18 R. T. Jackson, "Phvlogenv of the Pelecypoda," Menu Boston Soc. Nat. 

 Hist., Vol. 4, 1890. 



»A. W. Grabau, "Phylogenv of Fvsus and Its Allies." Smithsonian Misc. 

 CoB., Vol. 44, 1904. 



