'J4 University of California Publications in Zoology. [Vol. 6 



tn the question of how closely and in exactly what respects the 

 animals are adapted to their environment beyond the fact that 

 they must be generally so adapted, else they would not flourish. 



By turning, however, to another closely related species living 

 in a still different environment, we are enabled to push the in- 

 quiry farther, since we have then a differential In I in in tin or- 

 ganisms as well as In I in in lln environments. The new advan- 

 tage is in tlie circumstance that the question of linkage between 

 organism and environment is so much narrowed down and made 

 so much more definite. It now stands obviously this way: Do 

 the differences between If. haustor and 77. johnsoni correspond 

 to. and are they inseparably linked with, differences between 

 conditions of life in Puget Sound and San Diego Bay? Unfor- 

 tunately, imperfect as our information is about the water of 

 San Diego Bay. it is far more imperfect about the water of Puget 

 Sound. However, through the kindness of Mr. H. C. Stevens 

 of the University of Washing-ton, Seattle, Mr. MeEwen was able 

 to determine for me the specific gravity of one sample of water 

 from Elliot May. Puget Sound. This is shown in Table III. 



One question can now be asked in very specific terms : Do 

 the tubereulated, highly vascular test and the larger number 

 of tentacles of 77. johnsoni correspond to, in the sense of being 

 dependent upon, the higher density and temperature of water 

 in San Diego Bay? Undoubtedly one may conjecture such to 

 be the case. However, since there is no proof that higher tem- 

 perature does generally cause an increase in tentacle number, 

 such a conjecture would be a hypothesis; but again, since some 

 hypothesis of quite another character, for instance, that in- 

 creased tentacle number is an expression of general physiological 

 or growth tendency, has as much evidence to support it as has 

 the other, neither hypothesis would, it would seem, be justified 

 except for the purpose of being itself tested. It could not, that 

 is. be justifiably used as a support of some other broader, more 

 genera] hypothesis. 



The results arrived at in this last section are so largely nega- 

 tive and skeptical as to contain little of promise or encourage- 

 ment, at least so far as the questions of phylogenetic relationships 

 and causes of adaptive modifications are concerned. But just 



