72 Miss Agnes Crane — Evolution of the Brackiopoda. 



paper entitled, " Wbat is a Biachiopod ? " (29), issued in the 

 Geological Magazine two years later : he therein stated, ap- 

 parently considering the comparatively few species that survive 

 rather than the many that perished — "We have no positive evidence 

 of those modifications which the theory involves, for types appear 

 on the whole to be permanent as long as they continue, and when 

 a genus disappears there is no modification, that I can see, of any of 

 the forms that continue beyond so far as the Brachiopoda appear 

 to be concerned" (29). 



Two years later Joachim Barrande, a French Legitimist, and 

 formerly tutor to the Comte de Chambord, whose long exile from 

 France he shared in Bohemia, published an epitome of the general 

 results of his own vast labours in the Silurian system of Bohemia (1). 

 This distinguished palaeontologist stated independently that he could 

 adduce no evidence derived from his study of the Silurian Brachi- 

 opoda of Bohemia of the existence in that area of the modified 

 descendants of antecedent species (1), He therefore felt unable con- 

 scientiously to aflSrm from personal knowledge that the Brachiopoda 

 would be of much use in demonstrating the truth of the principle of 

 Evolution. Barrande died of grief a few days after the funeral 

 of his king and master, Henri Cinq King of France. But one would 

 hardly expect an adherent of the "white flag," a Legitimist, a believer 

 in the divine right of kings, to be a convert to Evolution. Allowance 

 must always be made for the personal equation and effects of the 

 environment. 



Davidson always admitted that varietal changes take place of 

 such a marked character as to make it diflScult to define the species, 

 and this led him to express the belief that such groups of species 

 were not of independent origin. He seemed thus to be convinced 

 of the extreme variation of certain species whilst maintaining the 

 permanence of genera. 



Now the tendency of all modern research appears to demonstrate 

 the extreme elasticity or flexibility of genera. At times uncertainty 

 prevails as to what constitutes specific, as distinct from generic, 

 characters. We are confronted with the problem of isomorphism, 

 or the apparent external similitude of species generically differen- 

 tiated by marked peculiarities of internal structure. So that we 

 often get species, heretofore referred on external characters to one 

 genus, split up into several genera or subgenera, based on divergent 

 characters of internal structui'e. The fossil Orthidce, for instance. 

 This occurs all along the line, for the recent species of what was 

 formerly termed the genus Waldheimia, of King, are now divided 

 into six or seven genera and subgenera; although, judging from 

 external characters alone, it is not always easy to differentiate them, 

 for specific features sometimes change less than generic ones. The 

 reasons for the separation are not fully apparent, until we come to 

 investigate the transitional stages of their individual development, 

 which reveal passing phases we may expect to find, nay often have 

 found, characterizing adult forms fossilized in antecedent strata. 

 Others are predicable — ^just as some of the earlier stages of the 



