1909] Ritter: Halocynthia johnsoni a.sp. 93 



the individuals of //. johnsoni living in these environments? In- 

 spection of the tabulated results of Miss Johnson's examination 

 of the specimens from the two Idealities given in Table I reveals 

 the fact that such differences do not appeal- within the range 

 of the observations made. If they exist at all, our studies must 

 be more searching to find them. We are consequently obliged 

 to conclude that so far as the fads ascertained go, there are 

 environmental differences within the natural habitat of this 

 species that arc without corresponding differences in the animals 

 subjected to them. 



We are not. of course, justified by the facts ascertained in 

 extending this conclusion to a general denial of such correspond- 

 ence. Since, however, we have examined these animals with at 

 least the usual fullness and care upon which prevailing concep- 

 tions rest about species in this group of animals, it would seem 

 that we are not justified in standing by a general hypothesis that 

 environmental differences must register themselves fully and ex- 

 actly in the structure and function of the organisms subject to 

 them, unless we are prepared to push our study of the organ- 

 isms to the point of recognition of such organic differences for 

 all the environmental differences which we can detect. 



Now suppose we accept this limitation — and, really, I do not 

 see how we can escape it. As soon as we do so. trouble of another 

 order comes in sight. Suppose we .should examine a lone' series 

 of specimens of //. johnsoni from the two localities here consid- 

 ered in far greater detail than we have the ones recorded, and 

 suppose we should find certain mean or average differences be- 

 tween the two lots, could we be sure that the differences between 

 the organisms were actually a register of the differences of the 

 two environments? But should we not have to do that in order 

 io sustain the hypothesis? It would seem so. 



This phase of the problem can be approached from another 

 direction. We have seen that //. johnsoni resembles rather 

 closely //. haustor of Puget Sound, the two being distinguishable 

 so far as at present known only by certain testicular characters 

 and the number of branchial tentacles. Since we have found 

 no differential characters as between specimens of //. johnsoni 

 living in different en\ ironments, we have no ground for an answer 



