LES BNCHAlNEMBKTS DU MONDE ANIMAL 95 



facts ; for example, the progress in the organ of 

 vision. Why should the primary Trilobites, with 

 their large compound eyes, furnished with thou- 

 sands of little facets, have been inferior to other 

 beings in the matter of perfection of sight ? Why 

 should the gigantic Phasmidae of the Coal period 

 have had sight less sharp than our present insects ? 

 For what reason should the Ichthyosaurs with 

 their enormous eyes have less easily pierced the 

 obscurity of the waters than our present Cetacea, 

 with eyes proportionately so much smaller ? Why 

 should the Jurassic Archceopteryx have had a less 

 piercing eye than the astonishingly perfect eyes of 

 our Birds ? The erroneous argument proceeds from 

 the comparison of qualities which are not com- 

 parable : each of the groups of the animal kingdom 

 possessed in geological times, as in our days, sensory 

 organs perfectly adapted to the environment for 

 which their use was required : the Agnostus of the 

 Cambrian Seas was blind because it dwelt in deep 

 seas where light did not penetrate, as in the same 

 way a large number of types of the deep-sea fauna 

 of the present day are blind. The Ichthyosaurus 

 and the Pterodactyl had large and very perfect 

 eyes, because that organ was indispensable to 

 them, as to our existing Raptores, in seizing their 

 prey. Progress, in all this, is not absolute, but 

 proportionate to the needs ; in other words, an 

 organ is perfect when it fulfils its object perfectly. 

 Notwithstanding these necessary restrictions to 

 the ideas of Gaudry on the details of the progress of 

 beings ideas steeped in an exaggerated, and at 

 times a somewhat artless sentimentalism it cannot 



