160 Report of the State Geologist. 



those of the framework of the extremities, and it furnishes a 

 new proof applicable to other animals. Among the Ruminant 

 Artiodactyls there exists a quite analogous series of fossils in 

 which the number of fingers passes from four to two by a 

 gradual regression of the two lateral fingers, while the molars 

 exhibit modifications entirely analogous to those in the horse. 

 There is then a correlation between the adaptation of the mem- 

 bers of the ungulates to running, and the specialization of their 

 teeth to an herbivorous diet. 



In both the cases mentioned, each of the characters separately, 

 distinguishing a perfect condition for the species, is explainable 

 by the theory of natural selection; whilst some other instances 

 of correlation, perfectly authenticated, are more difl&cult to 

 explain. Certain characters which are apparently useless to the 

 species, present sometimes a great variability; these are the 

 characters which the Darwinian school calls MorjpJiologic char- 

 acters. But it is undeniably established that they are in correla- 

 tion with characters of recognized utility to the species, varying 

 as these vary, and thus coming under the law of natural selec- 

 tion. Such,, for example, are the secondary sexual character- 

 istics, such as the beard of men, the long hair .of women, etc. 



Rudimentary organs. — According to Cuvier the principle of 

 correlation of forms was in contradiction to a great number of 

 facts which find their explanation only in the theory of selection. 

 If the animal possesses all that is necessary and nothing that is 

 superfluous for its existence in the condition in which it lives, 

 one can not conceive that it can possess organs which are mani- 

 festly of no service to it, and which are found better developed 

 and in a functional state in allied groups. Thus there sometimes 

 exist in man certain muscles which are at other times wanting, 

 but which are found well developed in the monkey. These rudi- 

 mentary organs are innumerable both in the animal and the 

 vegetable kingdoms. 



Palaeontology often explains to [us the significance of these. 

 The two stylets which are found on either side of the foot of the 

 Horse correspond to the two fingers, provided with all their parts, 

 of the Tertiary Equides. The Parrot possesses in the alveolus 

 embryonic teeth which never develop. But the three birds so 

 far known from the Secondary Epoch, Archceopteryx, Ichthyornis^ 

 and Eesperornis^ had conical, sharp-pointed teeth like those of rep- 

 tiles. We are acquainted, too, with instances of limbs, in a rudi- 

 mentary state, hidden under the skin of certain serpents, and 

 the existence of a very reduced pelvis in certain Cetacea, which 

 are furthermore, like the others, destitute of posterior limbs. 



