74 CALIFORNIA ACADEMY OF SCIENCES. 



orders and sundry lesser groups of the vertebrate king- 

 dom indicated; for, as already pointed out, the defini- 

 tions of such are radically placed in the different struc- 

 tures of the organs which aerate the blood and distri- 

 bute it to its various destinations. 



" But the great question: What determined the direc- 

 tion of this acceleration? remains unanswered. One 

 cannot understand why more highly oxidized blood 

 should hasten the growth of partition of the ventricle 

 of the heart in the serpent, the more perfectly to separate 

 the aerated from the impure fluid; nor can we see why 

 a more perfectly constructed circulatory system, sending 

 purer blood to the brain, should direct accelerated growth 

 to the cerebellum or cerebral hemispheres in the croco- 

 dile." 



The above statement of the cause of acceleration is 

 in reality no explanation, for after all the real question 

 is what determined the direction of the acceleration, for 

 which Prof. Cope does not here attempt to account. In 

 the paper on the Method of Creation of Organic Forms* 

 he offers another explanation, which appears to be final. 

 He asks, "What are the influences locating growth- 

 force?" and answers, " The only efficient ones with which 

 we are acquainted are: first, physical and chemical 

 causes; second, use; and I would add a third, viz.: ef- 

 fort." To this third influence Prof. Cope ascribes a 

 most important function that of originating new parts; 

 to it, indeed, may be attributed, according to Prof. Cope, 

 the origin of the fittest. He says: " You cannot rub 

 the sclerotica of the eye without producing an expan- 

 sion of the capillary arteries and corresponding increase 

 in the amount of nutritive fluid. But the case may be 

 different in the muscles and other organs (as the pig- 



* 1. c., p. 195. 



