THE DARWINIAN THEORY. 



97 



separately in different animals, e. g. Pterodactyles and birds — 

 Ichthyosauri and Cetacea*) — says that this is just what we would 

 expect, for, to take the Ichthyosauri, for example, it is apparent 

 that by Natural Selection and divergent variation they were 

 resolved into common fishes and Saurian reptiles, the inter- 

 mediate grades being extinguished in the struggle for existence 

 which ensued between the various species. 



[Poulton thinks that in the case of the large mammals pre- 

 ceding those which gave rise to the quadrupeds now upon the 

 earth, the small brains of the former were conspicuous, and he 

 thinks they were worsted by animals which were in other 

 respects no better endowed. In the same way the gigantic 

 reptiles of the Secondary Period were at a disadvantage with the 

 mammals of the Tertiary. Moreover, that Natural Selection 

 does not account for the beginning of things, and that there- 

 fore organs are formed by the modification of pre-existing 

 organs.] 



Darwin's drawing on the imperfection of the geological 

 record is met by the objection that our only ground for prophe- 

 sying what may come from such sources is by the analogy of 

 what has come to light. It is known that the last Ichthyosaurus 

 is hardly distinguishable from the first. The oldest Pterodactyle 

 is as thorough and complete as the most recent. Moreover, no 

 contrast can be more remarkable than the appearance of the 

 various species of Ichthyosaurus in the marine strata of the 

 chalk period, and the utter blank in reference to any form 

 calculated to throw light on their origin. 



[Prof. Haeckel, for the Darwinians, points out that physio- 

 logically Friedenthal has shown that the blood of man acts 

 poisonously on and decomposes the blood of the lower Apes and 

 other mammals, bat has not that effect on the blood of the 

 Anthropoid Apes. Selenka, again, demonstrated that certain 



* Cetaceans resemble Ichthyosaurians in non-union of the majority of the 

 ribs and sternum, in the peculiar articulation of the ribs with the vertebrae* 

 in the remarkable sternum itself, in the chevron bones of the caudal region, 

 late union of neural arches and bodies of vertebras, long symphysis of man- 

 dible, in the teeth, and in the absence or rudimentary condition of the pelvis. 

 Palaeontology reveals transition forms between Cetacea and Sirenia. Hali- 

 therium, again, links the Sirenia and hoofed animals. 



Zool. 4th ser. vol. XI 1 L, March, 2909. I 



