1897- COPE'S ''FACTORS OF EVOLUTION." 39 



of characters afterwards lost, Professor Cope cannot mean to deny that 

 there have been lines of progressive evolution {e.g. the Trimerellidae 

 among Brachiopoda and the Calceocrinidae among Echinoderma), 

 which rapidly became extinct; nor can he mean to deny that, in 

 the history of a line, a character (such as the coiling of Ammonoidea) 

 has gradually appeared and, as gradually, disappeared. What his 

 examples show him to mean is, that within the limits of any one 

 ascending series, there is no appearance of a character outside the 

 general trend of development. The inception and evolution of 

 characters are gradual processes, and a line of development once 

 started is continued. What is this, other than to say that variations 

 are so slight as to be imperceptible to our grosser sense ; that those 

 not in accord with environment are checked before they make their 

 mark on the history of the race ; that those in accord with environ- 

 ment are preserved ; and, since environment changes gradually and 

 definitely, that preserved variations and the consequent line of organic 

 evolution are also definite and gradual ? So far there seems nothing 

 in the statements of our author that may not be accepted with 

 untroubled conscience by the most orthodox of Neo-Darwinians. 



The final section of the same chapter can offend none except 

 those who would derive the Vertebrata from a highly specialised 

 arthropod, for it merely restates the fact that " the highly developed, 

 or specialised types of one geologic period have not been the parents 

 of the types of succeeding periods, but that the descent has been 

 derived from the less specialised of preceding ages." This, however, 

 does not even profess to bear on the main argument. 



Chapter III. is devoted to exemplifying what Professor Cope calls 

 the Canon of Parallelism. This, put as broadly as possible, and 

 without the qualifications that are required for each particular case, 

 states that " all organisms in their embryonic and later growth pass 

 through stages which recapitulate the successive permanent conditions 

 of their ancestry. Hence those which traverse fewer stages resemble 

 or are parallel with the young of those which traverse more numerous 

 stages." As an instance of this may be mentioned the case of the 

 lizard cited above ; but Professor Cope has had no difficulty in 

 adducing plenty of cases from various branches of the animal kingdom. 

 He further explains how inexact paralleHsm (caenogenesis of Haeckel) 

 may arise through certain characters developing more or less rapidly 

 in certain lines of descent than they do in others. Inexact parallelism 

 is, of course, the rule, while the necessity for compression in develop- 

 ment, or the opposing influence of an altered environment, has often 

 caused the partial or almost complete elimination from ontogeny of 

 recapitulatory stages. Accepting this most freely, still one cannot 

 shut one's eyes to the facts of parallelism, in many cases so obvious ; 

 and despite the amount of criticism that the principle has met with of 

 late, it really seems as though the only differences between the various 

 writers lay in their interpretation of admitted facts. What bearing he 



