215 



CORRESPONDENCE 



PROGRESS AND TRO VENDER 



Mr BERNARD modestly considers that the chief value of his entertaining paper "A 

 new reading in the Annulate Ancestry of the Vertebrata " {Nat. Sci., xiii., pp. 17-30, 

 July 1898) lies in its exemplification (whether rightly or wrongly) of a factor in evolu- 

 tion hitherto not sufficiently emphasised, namely, "that the profoundest morpho- 

 logical transformations leading to the rise of new groups of animals can be traced to the 

 adoption of new methods of feeding." Self-evident though the proposition seems, 

 "yet lam not aware," he continues, "that it has ever been applied systematically 

 except in the two cases in which I have myself endeavoured to apply it." From this 

 it appears that he is ignorant even of the title of Mr A. T. Masterman's suggestive 

 article "On some points in the general morphology of the Metazoa considered in con- 

 nection with the physiological processes of alimentation and excretion " (Zoo/. Anzeiger, 

 xix., pp. 190-198, 206-221, and 225-229—1896). On p. 228 of that paper, Mr Masterman 

 says, "Reasons have been given for regarding the modifications of the alimentary 

 processes to be the direct originators of other sets of organs, the instances of skeletal 

 and pigmentary organs being taken as typical. If in phylogeny the various organs 

 arise from and are intimately connected with, the alimentary processes, then in ontogeny 

 the same will result. The first signs of differentiation will appear in connection with 

 the sustentative function, and mechanical ingestive processes will lead the way." 



That modifications of the alimentary processes have been the chief guides in the 

 evolution of the classes of Echinoderma is a view that I never felt to be in need of 

 emphasis. It has however been emphasised by Dr Otto Jaekel, who says, "The 

 morphogeny of the Pelmatozoa depends essentially on two factors, on the one hand the 

 development of the nutrient ciliated grooves of the ambulacra, which soon results in 

 the formation of free arms, on the other hand those passive transformations which bring 

 about a correlation of those structures with the rest of the body" (Sitzber. Ges. naturf. 

 Freunde Berlin, 1894, p. 103). 



Mr Bernard will doubtless be glad to find that a view which he holds so strongly 

 and expresses so ably, is not likely to perish for lack of other support. 



F. A. Bather. 



"THE STUDY OF VARIATIONS." 



While not wishing to unnecessarily prolong this subject, I should be glad if you would 

 allow me to clear up some misconceptions in reference to the position I endeavoured to 

 maintain in your magazine for April and June. 



My position was based mainly on the immense difficulty experienced in determining 

 the value of small variations, and the fact, equally patent, that when this had been 

 accomplished there remained even more disputed questions in reference to the causes 

 which had led to their production. 



Instead of offering any theory of heredity, I merely put forward some suggestions 

 which I thought might explain the causes of this endless dispute : for this reason I en- 

 deavoured, as far as possible, to approach the subject from a neutral position. As a 

 matter of pergonal belief I think Mr Henslow and others have succeeded in demon- 

 strating that variations are more definite in nature than Darwin believed. I did not 

 need to state this conviction, because I provisionally accepted the facts adduced by Mr 

 Henslow himself, which therefore made it quite unnecessary to bring forward any other 

 evidence. 



While admitting that his explanation was, from his point of view, justifiable, it yet 

 appeared to me that the same facts were capable of explanation on another theory, which 

 was itself merely the nrc.ssii rij corollary of Natural Selection. Thus merely by continually 

 eliminating the less fit, and therefore leaving the more lit to survive and reproduce, the 

 average range of variability must increasingly tend towards perfect adaptability, in 

 exact proportion to the length of time and constancy of conditions operating on the 

 organism. On this hypothesis those forms of life which are subjected to continuous condi- 

 tions should have variations which are more definite in character than other forms 

 which have a more varied and less constant environment, hence plant life generally as 

 compared with animal should exhibit greater evidence of deliniteness in its variability, 



