ALPHEUS HYATT. 725 



These are the Lamarckian or dynamic agencies of use and disuse, brought 

 into action by environmental changes. 



" The efforts," he says, " of the Orthoceratite to adapt itself fully to the 

 requirements of a mixed habitat of swimming and crawling gave rise to 

 the Nautiloidea ; the efforts of the same type to become completely a 

 littoral crawler evolved the Ammonoidea. The successive forms of the 

 Belemnoidea arose in the same way. But here the ground-swimming 

 habitat and complete fitness for that was the object. The Sepioidea, on 

 the other hand, represent the highest aims as well as the highest 

 attainments of the Cephalopods in their evolution into surface-swimming 

 and rapacious forms. We cannot seriously imagine these changes to 

 have resulted from intelligent effort ; hut we can, with Lamarck and 

 Cope, picture them as due to efforts on the part of the animal to take up 

 new quarters in its environment and thus acquire habits and structures 

 suitable to the changed physical requirements of its surroundings, and 

 this position is better supported hy facts than any other hypothesis." 



Here are some examples of the complete and thoroughgoing way in 

 which Hyatt thought out, during his painfully slow but sure investiga- 

 tion of facts, broad generalizations which we feel confident will stand the 

 test of time and farther research. 



After speaking of " the effort to change of habitat and consequently 

 change of habits," due to change of environment, and of changes in 

 structure resulting from the efforts on the part of the organism to meet 

 the changes in the physical surroundings, he adds : " That this process 

 should end in the production of structures suited to the environment is 

 inevitable. With these factors at work, both without and within the 

 organism, the evolution of their structures obeys a physical law which acts 

 amid a thousand disturbing forces, perhaps, but nevertheless must act 

 with predominating force in one mean path or direction, the resultant 

 determined by the environment and the inherited structures of the 

 organism." 



Another beautiful research was his attempt to account by gravity for 

 the spiral shell of molluscs. He points out the fact of an obvious correla- 

 tion between the coiling of the shell and the habit of crawling. He 

 shows that those gastropod shells which degenerate and tend to lose the 

 spiral mode of growth and become irregularly straightened out in their 

 older stages of growth, are forms which become attached or which lead 

 sedentary lives, i. e. Vermetus attached late in life, and Magilus which 

 lives buried in coral. He points out the tendency in the descendants of 

 straight shells (Orthoceratites, etc.) to become, as the result of assuming 



