Bed active Gra nioloyy. 



15 



The divisions made between the contour of the orang and 

 that of the Andamanese skull, it will be seen, are in a decreasing 

 ratio from left to right. But as equal cranial expansions would 

 have increased superficial areas they would have diminished 

 thicknesses, otherwise the cubic contents of such expansions 

 would be unequal. The cranial divisions here given in a 

 diminishing ratio may thus be taken to express equal cranial 

 enlargements. 



The same reasoning would apply to the jaws, and consequently 

 equal degrees of jaw-diminution might have been expressed by 

 a series of divisions diminishing from right to left. An equal 

 division from A to A would express an increase in the rate of 

 jaw-diminution. In the diagram the divisions decrease from 

 left to right, and therefore the rate of jaw-diminution here 

 given is a diminishing rate. 



Taking the middle three of the links, namely, Nos. 4, 5, and 6, 

 the crania of which are seen to be not very far from the human 

 dimensions, the jaws are still wonderfully prognathous. Were 

 the rate of jaw-diminution an increasing one they would be still 

 more ape-like, ranging from beyond the jaws of No. 2 to under 

 No. 3 in the diagram. Were the rate of jaw-diminution equal 

 or pari passu with cranial enlargement, then the jaws would be 

 exceedingly ape-like, ranging from beyond No. 1 to between 

 Nos. 1 and 2 in the diagram. 



We thus see that when fossils of ape-like jaws are found, it 

 does not follow that they belong to true apes, as is concluded 

 by Mr. Lydekker 1 in the case of Palmopithecus, which may after 

 all belong to one of the "missing links"; as also may the 

 fossil Dryopithecus found in the south of France, near the base 

 of the Pyrenees. Indeed the more we consider the probabilities 

 of the form the more we are compelled to believe that the 

 majority of the transitional links must have been very prog- 

 nathous. 



As some people who have little faith in deductive methods 

 may ask wherein lies the advantage of endeavouring to find out 

 the forms of transitional links, I reply in anticipation that any 

 discovery must surely be aided by a previous knowledge of 

 what may reasonably be expected. 



The deductive method here adopted I claim to be a sound 

 one, and I have applied it further to the tracing of links between 

 other types of ape and human skulls, but the limited compass 

 of this brochure compels me to reserve the statement of my 

 results for a future paper. 



1 " Kecords of Geological Survey of India," vol. sii, Part I, p. 36. 



