September 10, 1909] 



SCIENCE 



325 



Several also assumed a shape of body and 

 limbs enabling them to live in the open sea. 

 Nearly all were cai-nivorous at first, and 

 most of them remained so to the end ; but 

 many of the Dinosaurs eventually became 

 practically hoofed animals, with a sharp 

 beak for cropping herbage, and with pow- 

 erful grinding teeth. In none of these ani- 

 mals, however, were the toes reduced to 

 less than three in number, and in none of 

 them were the basal toe-bones fused to- 

 gether as they are in cattle and deer. It is 

 also noteworthy that the brain in all of 

 them remained very small and simple. In 

 the final grade of backboned life, that of 

 the mammals, each of the adaptive modifi- 

 cations just mentioned began to arise again 

 in a more nearly perfected manner, and 

 now survival depended not so much on an 

 effective body as on a developing brain. 

 The mammals began as little carnivorous 

 or mixed-feeding animals with a small 

 brain and five toes, and during the Ter- 

 tiary period they gradually differentiated 

 into the several familiar groups as we 

 now know them, eventually culminating in 

 man. 



The demonstration by fossils that many 

 animals of the same general shape and 

 habit have originated two or three times, 

 at two or three successive periods, from two 

 or three continually higher grades of life, 

 is very interesting. To have proved, for 

 example, that flying reptiles did not pass 

 into birds or bats, that hoofed Dinosaurs 

 did not change into hoofed mammals, and 

 that Ichthyosaurs did not become por- 

 poises; and to have shown that all these 

 later animals were mere mimics of their 

 predecessors, originating independently 

 from a higher yet generalized stock, is a 

 remarkable achievement. Still more sig- 

 nificant, however, is the discovery that 

 towards the end of their career through 

 geological time totally different races of 

 animals repeatedly exhibit certain peculiar 



features, which can only be described as 

 infallible marks of old age. 



The growth to a relatively large size is 

 one of these marks, as we observe in the 

 giant Pterodactyls of the Cretaceous 

 period, the colossal Dinosaurs of the Upper 

 Jurassic and Cretaceous, and the large 

 mammals of the Pleistocene and the pres- 

 ent day. It is not, of course, all the mem- 

 bers of a race that increase in size ; some 

 remain small until the end, and they gen- 

 erally survive long after the others are ex- 

 tinct; but it is nevertheless a common rule 

 that the prosperous and typical representa- 

 tives are successively larger and larger, as 

 we see them in the familiar cases of the 

 horses and elephants of the northern hem- 

 isphere, and the hoofed animals and arma- 

 dillos of South America. 



Another frequent mark of old age in 

 races was first discussed and clearly 

 pointed out by the late Professor C. E. 

 Beecher, of Yale. It is the tendency in all 

 animals with skeletons to produce a super- 

 fluity of dead matter, which accumulates 

 in the form of spines or bosses as soon as 

 the race they represent has reached its 

 prime and begins to be on the down-grade. 

 Among familiar instances may be men- 

 tioned the curiously spiny Graptolites at 

 the end of the Silurian period, the homed 

 Pariasaurians at the beginning of the Trias, 

 the armor-plated and horned Dinosaurs at 

 the end of the Cretaceous, and the cattle or 

 deer of modern Tertiary times. The latter 

 case— that of the deer— is specially inter- 

 esting, because fossils rcA'eal practically all 

 the stages in the gradual development of 

 the horns or antlers, from the hornless con- 

 dition of the Oligocene species, through the 

 simply forked small antlers of the Miocene 

 species, to the largest and most complex of 

 all antlers seen in Cervus sedgwicki from 

 the Upper Pliocene and the Irish deer (C. 

 giganteus) of still later times. The growth 

 of these excrescences, both in relative size 



