XINKEAN SOCIETY OF LONDOK. II 



The paramount importance of the development of the central 

 nervous system for the upward progress ot the members of the 

 Animal Kingdom leads to the conclusion that each higher group of 

 animals has arisen in succession from the highest race developed 

 up to that time, by highest meaning the group possessing the best 

 developed central nervous system. This law is proved to us most 

 clearly by the evidence of the rocks in the case of the Vertebrate 

 group. 



Thus we see that Man came from the Mammals, tlie highest 

 race in the Tertiary times. They arose from the Keptiles, the 

 highest race in Mesozoie times, who in their turn arose from the 

 -Amphibians, the lords of the Carboniferous epoch. Further back 

 we leave the land and find that the Amphibians arose from the 

 Fishes, the earliest of the Vertebrate race which swarmed in 

 Devoniau times. This steady sequence in upward progress from 

 Fishes to ]\Ian, revealed by Geology in the long series of ages 

 from the Devonian to recent days, is in absolute conformity with 

 the upward development of brain-power through the Vertebrate 

 series from Fishes to Man, as shown by the investigations of 

 Comparative Anatomists, especially Edinger and Elliot Smith. 



If thus it can be proved that such a law of Evolution has held 

 good through the enormous spaces of time between the beginning 

 of the Devonian and the present day, surely it is highly probable 

 that the same law has held thz'oughout, and that therefore the 

 Fishes themselves arose from the race that was the most highly 

 developed at the tune when they first appeared; a race therefore 

 which possessed a central nervous system most closely resembling 

 that of the fish. 



The evidence of the rocks points to the Silurian age as the time 

 when the Vertebrate first arose, and to the great and striking group 

 of Arthropods which swarmed in the seas at that time, to which 

 the name Palceostraca has been given. These were the highest 

 developed race at that time and from them, according to this law 

 of Evolution, the Vertebrate ought to have sprung. 



The great problem then for the study of the origin of Vertebrates 

 resolves itself into this : What was the nature of the earliest fish 

 aud of the Palaeostraca in Silurian times ? 



That was the problem I set myself, and it is that comparison 

 which I have attempted organ by organ in my recent book. Such 

 an attempt Avas rendered possible by the fortunate occurrence of 

 one of the Palaeostracau Group — Linmlus or the King Crab — being 

 still living in the present day, and what is still more important, 

 the remarkable resemblance of Ammocoetes — the larval form of the 

 Lamprey — to the fishes belonging to the Osteostraci, especially the 

 close resemblance in position and structure of that remarkable 

 muco-cartilaginous head-shield of Anvnoccetes to the head-shield 

 of such a fish as Cephalasjns. 



My object throughout has been by the study of Ammocoetes to 

 find out a clue to the past history of these extraordinary early 

 forms of fish. The results are published in my book, and give a 



