May 4, 1906.] 



SCIENCE. 



689 



I will admit that Dr. Merriam's explana- 

 tion of his facts may be true, but he did 

 not convince me of its correctness any more 

 than Professor Hyatt convinced me of the 

 correctness of his interpretation in his 

 ' Phylogeny of an Acquired Characteristic. ' 

 His facts seem just as plausibly explicable 

 on the basis of the Darwinian hypothesis 

 or that of de Vries. According to the 

 former those variations tending to give the 

 species an advantage in the struggle for its 

 life would be preserved, while other varia- 

 tions would be eliminated. This preserva- 

 tion of certain individuals and the elimina- 

 tion of others would cause divergence in 

 the characters of the occupants of the re- 

 spective areas. In the intermediate zone, 

 as there would not be definite selection, 

 there would not be distinct diiferentiation 

 of type. 



The de Vries hypothesis will explain 

 them just as well. The forms occupying 

 the respective areas may have originated 

 by mutation, and the intermediate zone 

 may be occupied by hybrids. 



The evidence in favor of none of these 

 h5T)otheses is conclusive. 



The facts presented by Dr. Merriam are 

 a necessary foundation for the recognition 

 of the factors involved in the problem, but 

 they do not solve the problem. I should 

 like to know : 



1. Something concerning the stability of 

 the characters of the forms inhabiting the 

 different areas. 



In this connection the following ques- 

 tions may be asked: 



(a) Is the difference observed between 

 the individuals occupying the different 

 areas caused by the direct influence of 

 physical environment? If the difference 

 is caused by such influence, is the change 

 so wrought only superficial or is it hered- 

 itarily transmissible? The feathers of 

 birds exposed to strong sunlight are of 

 lighter color than those of birds living in 



areas in which the light is weaker. From 

 characters of this kind we can infer that 

 the specimens exhibiting them lived under 

 certain conditions. Do changes of this 

 kind extend to the gametes of the indi- 

 vidual or are they only somatic changes, 

 enabling us to infer that an individual 

 lived under certain physical conditions, 

 similar to the inference drawn from seeing 

 a man with certain scars on his face, viz., 

 that he has attended a German university ? 



Dr. Dall, in his review of Gulick's 

 'Evolution, Eacial and Habitudinal, ' says 

 concerning the theory of segregation advo- 

 cated by that author: 



To justify i5nal acceptation an hypothesis must 

 not only be capable of accoimting for the facts, 

 but it must be shown to be the only one by which 

 they may be adequately explained. It is also 

 necessary to determine how far the animals in 

 question have arrived at that state of equilibrium 

 which we recognize by the name of species. If, 

 as has been held by some authorities, the small 

 color groups are really only of a temporary na- 

 ture, and liable to iromediate change upon sub- 

 jection to modified environment, then the au- 

 thor's hypothesis, while losing none of its truth, 

 is not a contribution to the evolution of species 

 so much as to the physiology of color variation. 



(&) Should the differences be gametic in 

 origin, i. e., not induced by the physical 

 environment, is the selection between di- 

 vergent variations of one species; or is it 

 between two different species? 



I could present a series of observed phe- 

 nomena in the Madreporaria parallel to 

 some of the data presented by Dr. Merriam 

 in his discussion of the distribution of 

 mammals and birds. These instances could 

 be drawn from several genera, but those 

 from Turhiiiaria are especially a propos. 

 Mr. Pace has carefully studied these corals 

 in the Torres Straits; he, however, dis- 

 cretely remarks : 



It will now be my endeavor to show that the 

 variations of a turbinarian colony from the primi- 

 tive cup-shape — the ' crateriform ' type of Ber- 

 nard — can be readily explained by reference to the 



