No. 506] KELPS AND RECAPITULATION THEORY 103 



with Marchantia. Such primitive types are few and 

 far between for obvious reasons: if an entire group 

 advances rapidly it moves up bodily into a higher 

 plane and leaves behind only such forms as stray into 

 some byway of specialization, which specialization would 

 be a bar to future progress except in the line upon which 

 the form had entered. All unspecialized forms left be- 

 hind in the advance of the race are likely to be displaced 

 early in the struggle for existence because of their lack 

 of particular adaptations. It is accordingly only in such 

 environments as present no specialized demands upon 

 their inhabitants that we may expect to find these prim- 

 itive forms and it will be observed that to a large extent 

 such is the case. 



Wherever a form is found with simple unspecialized 

 structure it becomes at once a problem to decide whether 

 it is in reality primitive or a degenerate type. If there 

 is no paleontological history to aid in the solution a con- 

 clusive answer to this question is often impossible. How- 

 ever, unless there is definite evidence of degeneration m 

 vestigial structures or the like, as there is in many cases, 

 for example the mistletoes ; it is generally safe to assume 

 that the present condition of the organism represents 

 its highest attainment in the process of evolution. De- 

 generate forms usually manifest a high degree of fixity 

 in their organizations and great variability is seldom 

 found in such forms: It might be suggested that the 

 apparently primitive structure of Renfrewia may be due 

 to degeneration from a condition more highly differen- 

 tiated. It possesses, however, no vestigial or united 

 organs, with the exception of the basal cone of the stipe. 

 Every portion of the plant is functional. There are 110 

 peculiarities about its structure which mark it as difter- 

 ent from the other kelps. On the contrary, its ivpn.du,- 

 tion and its histology are similar to them. Its ha " 

 quiet water just below the tide mark, is exactly that \\ n< ^ 

 would be expected of the ancestors of the kell> ^ i ^ 

 they acquired adaptations enabling them to en ure i 



