236 Recent Literature. [ April, 
dinavian, and the Porcupine and Challenger, and other English expedi- 
tions. We are disposed to find some fault with the present work in not 
considering the subject from a stand-point so important as this. 
To return to the theory as to the origin of the present distribution of 
life on the great continents by means of a migration from lands to the 
north. While the idea is evidently original with Mr. Wallace, he 
seems to have overlooked some suggestions made by writers in the United 
States previous to the publication of his work. More than twenty years 
ago Professor Asa Gray! proposed the hypothesis that the present 
vegetation of North America “or its proximate ancestry must have 
occupied the arctic and subarctic regions in Pliocene times, and that it had 
been gradually pushed southward as the temperature lowered and the 
glaciation advanced even beyond its present habitation.” He also at- 
tempted to show that certain forms might survive in Japan and the 
Atlantic United States, “ but’ not in intermediate regions of different 
distribution of heat and moisture.” . . . . And it was thought that the 
occurrence of peculiarly North American genera in Europe in the Ter- 
tiary period (such as Taxodium, Carya, Liquidamber, Sassafras, Negundo, 
ete.) might be best explained on the assumption of early interchange and 
diffusion through North Asia rather than by that of the fabled Atlantis.” 
These views were confirmed by Lesquereux. In 1873 the reviewer applied 
this hypothesis to the origin of the distribution of animals, particularly in- 
sects.” We then, in dircussing the origin of our North American fauna, 
drew the inference that “cospecific or congeneric forms occurring in 
California and Europe and Asia are the remnants of a southward migra- 
tion from polar Tertiary lands during Tertiary and even perhaps Creta- 
ceous times, and in proportion to the high antiquity of the migrations 
there have been changes and extinctions causing the present anomalies 
in the distribution of organized beings, which are now so difficult to 
account for on any other hypothesis.” 
As Mr. Wallace could not in such a work enter into details of distri- 
bution beyond briefly describing his subregions, in which temperature and 
natural barriers need to be studied with care, he may have been led into 
the error of underestimating the influence of zones or temperature 1m 
determining the limits of distribution within the subregions. Much 
excellent work that has been done in this direction by American natu- 
ralists, who have had much better opportunities than European students, 
has been too hastily discussed either from want of space or from lack of 
information, since the great extent of North America as compared with 
that of Europe is exceedingly favorable to the formation of correct op!- 
ions regarding the influence of climate on species, an influence of greater 
1 Memoirs of the American Academy of Arts and Sciences. Boston. Vol. 6. See 
Sequoia and its History, American Naturalist, October, 1872, pp- 589, 590. . 
2 On the Distribution of Californian Moths. By A. S. Packard, Jr. American 
Naturalist, August, 1873, and Proceedings of the Boston Society for May, 1873. 
