ON THE COMMON PLAN OF ANIMAL FORMS 283 



The Lecturer here drew an illustration from Philology — a science 

 which in determining the affinities of words also employs the method 

 of gradation. Thus miiis, uno, un, one, ein, are said to be modifications 

 of the same word, because they pass gradually into one another. So 

 Hemp, Hennep, Haiif, and Cannabis, Canapa, Chanvre, are respectively 

 modifications of the same word ; but suppose we wish to .make out 

 what, if any, affinity exists between Hemp and Cannabis — the method 

 of gradation fails us. It is only by all sorts of arbitrary suppositions 

 that one can be made to pass into the other. 



Nevertheless modern Philology demonstrates that the words are 

 the same, by a reference to the independently ascertained laws of 

 change and substitution for the letters of corresponding words, in the 

 Indo-Germanic tongues : by showing in fact, that though these words 

 are not the same, yet they are modifications by known developmental 

 laws of the same root. 



Now Von Bar has shown us that the study of development has a 

 precisely similar bearing upon the question of the unity of organization 

 of animals. He indicated, in his masterly essays published five-and- 

 twenty years ago, that though the common plans of the adult forms 

 ■of the great classes are not identical, yet they start in the course of 

 their development from the same point. And the whole tendency of 

 modern research is to confirm his conclusion. 



If then, with the advantage of the great lapse of time and progress 

 of knowledge, we may presume to pronounce judgment where Cuvier 

 and Geoffroy St. Hilaire were the litigants — it may be said that 

 Geoffroy's inspiration was true, but his mode of working it out false. 

 An insect is not a vertebrate animal, nor are its legs free ribs. A 

 cuttlefish is not a vertebrate animal doubled up. But there was a 

 period in the development of each when insect, cuttlefish, and 

 vertebrate were undistinguishable and had a Conimon Plan. 



The Lecturer concluded by remarking that the existence of hotly 

 controverted questions between men of knowledge, ability, and 

 especially of honesty and earnestness of purpose, such as Cuvier and 

 his rival were, is an opprobrium to the science which they profess. 

 He would feel deeply rewarded if he had produced in the minds of 

 his hearers the conviction that these two great men — friends as they 

 were to one another — need not be set in scientific opposition ; that 

 they were both true knights doing battle for science ; but that, as the 

 •old story runs, each came by his own road to a different side of 

 the shield. 



