ST. IHLAIRE. 201 



As it involved rapid, as well as gradual, transfor- 

 mation, St. Hilaire's system did not alwavs rccjuire 

 the existence of intermediate links. Vox instance, 

 he advanced as an hypothesis the suggestion that 

 the first bird might have issued directly from the 

 ^%% laid by a reptile, and, as a bird could not be fer- 

 tilized or intercrossed by its reptilian relatives, the 

 new characters could not be supjDressed by inter- 

 crossing: "It is evidently not by an insensible 

 change that the inferior types of oviparous verte- 

 brates have given rise to the superior organization of 

 the group of birds. An accident, within the ran<rc 

 of possibility, and not very great in its original pro- 

 duction, but of an incalculable importance in all its 

 effects, has sufficed to produce in all parts of the 

 body the conditions of the bird type." 



Finally, his attitude towards transformism, as 

 explaining all forms of life, was much less positive 

 and sweeping than Lamarck's. His view of Evo- 

 lution may be summed up in this sentence : " Spe- 

 cies vary with their environment, and existing 

 species have descended by modification from earlier 

 and somewhat simpler species." He admitted that 

 the question to be decided by future paleontological 

 research, is whether " the living forms of to-day 

 have descended by a succession of generations, and 

 without break, from the extinct forms of the ante- 

 diluvian period." He looked for, and found, proofs 

 and evidences, within his own reach, in limbryology, 

 in the history of metamorphoses and in Teratology. 



