188 Reports & Proceedings — Edinburgh Geological Society. 



Runcorn, in the neighbourhoods of Frodsham, Ince, and Ellesmere 

 Port, some of which reached a depth of over 900 feet below the 

 surface. At Ellesmere Port evidence has been obtained of an 

 important trough fault, and the thickness of the drift has been 

 proved to be as much as 113 feet. None of the boreholes 

 passed beyond the Lower Bunter Sandstone. 



III. — Edinbuegh Geological Society. 



January 22, 1919. (Received February 14.) — Professor Jehu, 



President, in the Chair. 



1. "The Origin of Terrestrial Vertebrates." By the President, 

 Professor T. J. Jehu. 



The ancestry of vertebrates is still an unsolved problem, and 

 palaeontology can throw little light on the subject. One theory 

 traces their descent through a series of primitive Chordate forms 

 represented by Amphioxus, the Tunicata, and Balatwglossus. The 

 peculiar ciliated larva of Balanoglosstis, known as Tornaria, shows 

 marked resemblances to the larvse of the echinoderms, and a form 

 similar to this larva may possibly have been the common ancestor of 

 echinoderms and vertebrates. Another hypothesis derives the 

 vertebrates from the Annelida, the organs of which show a curious 

 correspondence, but with a general reversal of the relation of the 

 various parts to one another. A recent theory seeks the vertebrate 

 ancestor amongst the more primitive arachnoids, now represented by 

 Limulus, and formerly exhibited by the extinct group of Merostomata. 

 Chamberlin's theory is that the vertebrates originated in flowing land 

 waters as a response to the influence of strenuous dynamic conditions 

 impressed upon a primitive animal aggregate towards the close of 

 pre-Cambrian times. The return of migratory fishes to rivers for 

 spawning purposes is an argument in favour of regarding flowin 

 land waters as their ancestral home. Primitive armoured fishes are 

 found in Ordovician sediments in Western America, and more typical 

 fishes appeared in Europe towards the close of the Silurian period 

 and became abundant in Old Eed Sandstone times. The appearance 

 of fishes which utilized the air-bladder for respiratory purposes at 

 this period was the result of adaptations to oscillations of climate 

 leading to alternate seasons of drought and rain. The life-habits 

 of Dipnoans and fringe-finned Ganoids which have survived as relic 

 fauna to the present day were described. These afford a clue to the 

 conditions of life which, during Devonian time, led to lung-breathing 

 in the Dipnoans and Ganoids of that period. Increasing aridity of 

 climate eventually led to the emergence of vertebrates from their 

 aquatic habitat and their adaptation to life on land. This transition 

 is illustrated in the Amphibia which appeared at the close of the 

 Devonian period and developed into diverse forms during the 

 Carboniferous. The fact that the early life of amphibians is aquatic 

 and that for a time they breathe by means of gills, shows that they 

 were not completely adapted to a terrestrial life. The Stegocephalia 

 show more resemblances to the fringe-finned Ganoids than to the 

 Dipnoans, especially in the structure of the limbs, and more probably 



