LAW OF PARALLELISM 93 



evolution caused by forces inherent in the organism. " The 

 transformations," he writes, "which have determined the 

 most remarkable changes in the number and development 

 of the instruments of organisation are incontestably much 

 more the consequence of the tendency, inherent in organic 

 matter, which leads it insensibly to rise to higher states 

 of organisation, passing through a series of intermediate 

 states." 1 



His final enunciation of the law of parallelism in this 

 same volume shows that he considered the development of 

 the individual to be due to the same forces that rule evolu- 

 tion. " The development of the individual organism obeys 

 the same laws as the development of the whole animal series ; 

 that is to say, the higher animal, in its gradual evolution, 

 essentially passes through the permanent organic stages 

 which lie below it ; a circumstance which allows us to assume 

 a close analogy between the differences which exist between 

 the diverse stages of development, and between each of the 

 animal classes" (p. 514). 



He was not, of course, able fully to prove his contention 

 that the lower animals are the embryos of the higher, and 

 we gather from the following passage that he could maintain 

 it only in a somewhat modified form. " It is certain," he 

 writes, " that if a given organ shows in the embryo of a 

 higher animal a given form, identical with that shown through- 

 out life by an animal belonging to a lower class, the embryo, 

 in respect of this portion of its economy, belongs to the class 

 in question " (p. 535). The embryo of a Vertebrate might 

 at a certain stage of development, be called a mollusc, if for 

 instance, it had the heart of a mollusc. 



He admits, too, that the highest animal of all does not 

 pass through in his development the entire animal series. 

 But the embryo of man always and necessarily passes 

 through many animal stages, at least as regards its single 

 organs and organ-systems, and this is enough in Meckel's 

 eyes to justify the law of parallelism (p. 535). 



In his excellent discussion of teratology Meckel points 

 out how the idea of parallelism throws light upon certain 



1 From the French trans., which appeared under the title Traite gen. 

 d'Anat. compare'e, i.^ p. 449, 1828, 



