BIOLOGY. 311 



to Darwin's work on " The Variation of Animals and Plants 

 under Domestication," and to the review above quoted. 



ORGANIC PROGRESSION OF ANIMALS OF THE SAME FAMILY. 



M. Ed. Lartet, in " Comptes Rendus " for June, 1868, draws at- 

 tention to the gradual modification in course of time of various 

 organs, especially among the ruminants, with the results of in- 

 crease of functional energy in special directions, and a real prog- 

 ress in the animal existence of modern times. 



In the oldest cervidce of the tertiary epoch, the enamelled crown 

 of the molar teeth above the neck is much lower, and less promi- 

 nent beyond the alveolar ridge, than in the quaternary and actual 

 deer of this family ; so that the tortuous folds of enamel, which 

 form the triturating surface of these teeth, are so shallow that the 

 bottom can always be seen in the former, but never in the latter. 

 This is a useful and certain diagnostic mark for the paleontologist, 

 and is applicable also to other herbivora, pachyderms, rodents, 

 and omnivora. 



In the genus cervus, the molars cease to grow after the crown is 

 fully developed, and, as this crown is worn away by daily use, 

 the functional duration of these teeth depends on their greater or 

 less elevation above the alveolus ; hence it may be legitimately 

 concluded that the ancient tertiary cervidce, whose molars had 

 crowns much less elevated than the later and living species, had a 

 shorter period of life, as the longevity of an animal depends essen- 

 tially on the functional duration of the organs necessary for nutri- 

 tion. 



It is also a result of his observations that, the older the animal 

 in tertiary time, the smaller becomes the brain in comparison with 

 the size of the head and the dimensions of the body. The in- 

 ferior character of the brain of anoplotherium was long ago ob- 

 served by Cuvier; in fact, the head of this animal, of the size of 

 an average ass, was six times as long as the impression of its 

 cerebral hemispheres, and its brain was smaller than that of the 

 existing roebuck. As we approach the present epoch, the differ- 

 ence between fossil and recent brains becomes less marked, as 

 does the elevation of the crown of the molar teeth. In the brains 

 of deer and antelopes of the middle miocene of Sansan many con- 

 volutions are seen, but the cerebellum is little covered by the hem- 

 ispheres, and the olfactory lobes are largely developed ; in the 

 upper miocene of Pikermi the brain of hipparion is less rich in 

 convolutions than in the existing horse. This fact is more marked 

 in animals of the same genus ; in the viverra antiqua of the lower 

 miocene of Allier as compared with the living V. genetta, the for- 

 mer, with a cranium a third longer and a fourth wider than in the 

 latter, had no larger brain, and one at the same time with thinner 

 frontal folds, a less development toward the face, and a large size 

 of the olfactory lobes. Paleontology proves the truth of the re- 

 mark of Gratiolet, that a great development of the olfactory lobes 

 is a mark of an inferior type. 



