468 T. H. MOEGAN. 



is so similar to the method of elongation of the Annelid body 

 that even the most casual observer must be impressed by the 

 comparison. The greatest drawback to any attempt to refer 

 the two cases to a common method of growth (not phylo- 

 genetic^ of course) would probably be met l\v the statement 

 that the repetition of a metamere is something entirely 

 diflPerent from the repetition of the vertebral ridge in the star- 

 fish's arm. If we can succeed in breaking down this conven- 

 tional and artificial definition of the value of metaraeric 

 repetition as compared with other repetitions of the body we 

 shall have made a step forward I am confident. This question 

 will be more fully dealt with in the next section. 



I have asked the opinion of eminent botanists on several 

 occasions as to the meaning of the repetition of the parts of 

 the higher plants, particularly the Phanerogams. So far as I 

 can learn, the botanical phylogenists have not had a much 

 better time of it than the zoological phylogenists. The former 

 have had the immense advantage of much palseontological ma- 

 terial, but, as I understand, even with this the great gaps come 

 just where the evidence is most wanted. I have not, however, 

 found any botanist who believed that in the past a single stem 

 and leaf or two leaves (phytomeres) represented the ancestral 

 plant which grew long by repeating itself, as the embryo 

 plant does at present. 



Haeckel, in his ' Generelle Morphologic/ 1866, used the 

 term " promorphology " to include the fundamental relations of 

 the parts of an animal to one another, in the same sense that 

 the relations of the axes of a crystal are the expression of its 

 form. The aim of promorphology, Haeckel said, is to deter- 

 mine the ideal fundamental form by a process of abstraction, 

 and to discover the natural laws according to which organic 

 matter develops its outer form. The relation of the parts, i.e. 

 the form, results with absolute necessity from the architectural 

 union of the constituent parts, in the same sense that an inor- 

 ganic crystalline form results from the union of crystalline 

 material, and from its relation to its environment. 



Whether morphology will be ultimately driven to an inter- 



