j^^ THE ANIMAL KINGDOM. 



In The American Naturalist, for December, 1871, the writer assumed, from a 

 study of cave animals, that these forms were suddenly produced, though the changes 

 may not have been wrought until, say, after several thousand generations ; and the theory 

 of Cope and of Hyatt, of creation by a process involving the idea of accelerated de- 

 velopment in some species, and retarded development in certain organs of other species, 

 was adoi.ted. These views were again enforced in Hayden's Bulletin of the United 

 States Geological Survey (April, 1877), in an article on the Cave Fauna of Utah. 

 In 1872 the writer (Development of Limulus), from a study of the paleozoic 

 Crustacea and of the development of Limulus, claimed that it was impossible " that 

 at the dawn of silurian life these well-marked groups were due entirely to tlie extinc 

 tion of multitudes of connecting links, such as Mr. Darwin assumes to have been 

 evolved on the principle of natural selection, with the subordinate agency of sexual 

 selection and mimicry, etc. The groups are almost as clearly marked as in the present 

 time, and such a theory seems to us inadequate to account for the rise of such distinct 

 forms, apparently simultaneous in their appearance at the beginning of the silurian. 

 The forms are remarkably isolated, and present every appearance of having been in a 

 degree suddenly produced," i. e., by differences in the temperature and depth of the 

 water, etc., the differences being due to changes in the physical surroundings of the 

 organisms. Farther on it is stated : " I conceive these differences to be due, perhaps, 

 to sudden changes of temperature in fresh-water pools, to the difference in the density 

 of fresh and salt w\ater, and the liability of fresh-water pools to dry up, combined with 

 less apparent causes." It will be seen that these views essentially agree with what is 

 known as Lamarckianism. In his Monograph of the Geometrid Moths, the writer 

 attempted to show that climatic and geological causes were important factors in the 

 production of the genera and species constituting the different faunas. 



That changes in the physical surroundings of the organism, rather than the strug- 

 gle for existence among the animals themselves, jn-oduce new forms of animal life, 

 was also insisted upon by the writer (Half Hours with Insects, 187G), in the follow- 

 ing words : — 



" When one looks at the beds of fossil beings of the earlier geologic periods, he 

 peers into the tombs of millions which could not adapt themselves to their constantly 

 changing surroundings. No fossil being is known to us which could not have been as 

 well adapted to its mode of life as the animals now living ; but the conditions of life 

 changed, and the species, as such, could not withstand the possible influx of new forms, 

 due to some geological change which induced emigration from adjoining territories, or 

 to changes of the contour of the surface, with corresponding climatic alterations. 

 Let one look at the geological map of North America before the cretaceous period, 

 ere the Rocky Mount.iins appeared above the sea, and reflect on the remarkable changes 

 that took place to the northward, — the disappearance of an Arctic continent, the re- 

 ]>lacement of a tropical climate in Greenland and Spitzbergen by Arctic cold. Are 

 there not here changes enough in the physical asjjects of our country to warrant such 

 hyjwtheses of migrations, with corresponding extinctions and creations of new faunas 

 out of preceding ones, as are indulged in by naturalists of the present day, in the light 

 of the knowledge pouring in upon them from Arctic explorers and western geologists? 

 Granted these extraordinary clianges in the physical surroundings of the animals 

 whose descendants people our land, do not a host of questions arise as to the result, in 

 the beings of our day, of these changes in the modes of life, the modes of tliought, so 

 to sjieak, the formation of peculiar instincts arising from new exigencies of life, which 



