346 



SCIENCE 



[N. S. Vol. XXXIV. No. 872 



engineering; Hex E. Edgecomb, B.S. (C. E.) 

 (Iowa State), instructor in civil engineering; 

 Charles D. Fawcett, B.S. (E. E.) (Colorado), 

 instructor in electrical engineering; Frank S. 

 Bauer, B.S. (M. E.) (Illinois), instructor in 

 mechanical engineering ; Herbert D. McCaslin, 

 B.S. (M. E.) (Purdue), instructor in mechan- 

 ical engineering; J. B. Hanson, A.B. (Mis- 

 souri), instructor in physiology and pharma- 

 cology. 



DISCUSSION AND COBBESPONDENCE 



M. COSSMANN ON THE PHYLOGENY OF CERITHIUM 



In the Revue Critique de Paleozoologie for 

 April, 1911, M. Cossmann published a review 

 of my paper on " The Phylogeny of Certain 

 Cerithiidae " which involves a question of 

 fundamental principles in the study of 

 phylogeny and is therefore of interest to con- 

 sider at greater length. 



M. Cossmann calls attention to the fact 

 that my classification differs widely from that 

 published in his monograph on the Cerithi- 

 idse.' The reason for this is, as stated in my 

 paper, that we are following entirely different 

 methods of work. We are, I think, in accord 

 in assuming that a natural classification 

 should be based upon descent from a com- 

 mon ancestor but as to the principles to be 

 followed in determining relationship we differ 

 widely. M. Cossmann's classification is 

 based on a comparison of the aperture and 

 especially of the " cerithial " canal, mine 

 upon the entire ontogeny of the shell, the 

 facts thus obtained being applied in accord- 

 ance with Haeckel's biogenetic law. M. 

 Cossmann's argument in favor of using the 

 aperture as a basis of classification is stated 

 in his review as follows : " C'est par I'ouver- 

 ture que sortent les organes d'un Gastropode, 

 c'est par la que son manteau secrete le test; 

 c'est done I'ouverture qui joue le principal 

 role dans revolution." It is true that the 

 mantle secretes the shell at the aperture, but 

 if the adult aperture be considered of so 

 much importance how can we neglect the suc- 

 cession of apertures represented by the young 



'M. Cossmann, "Essais de Paleoconchologie 

 Comparee," VII., July, 1906. 



shell every growth line of which outlines the 

 aperture of the shell at the time when the 

 line was formed. If it be true, as stated by 

 Hyatt,'' that " All modifications and variations 

 in progressive series tend to appear first in 

 the adolescent or adult stages of growth " we 

 shall find in the adult aperture the extreme 

 limit of variation for the individual, and it is 

 to this stage that we look for divergence from 

 the well established, hereditary characters 

 that ally the organism with its ancestors. If 

 recapitulation be a fact it is in the young 

 stages that inherited characters find their 

 fullest expression. A defense of the methods 

 used in my paper and of my results is simply 

 a defense of the theory of recapitulation, and 

 no adequate presentation of the subject can 

 be attempted in a limited space. The validity 

 of the theory is still questioned by some 

 scientists, mainly zoologists, but the final 

 answer to the question will be, as in the case 

 of the theory of evolution itself, an accumu- 

 lation of corroborative facts so overwhelming 

 as to finally silence doubt. Already the ac- 

 cumulation of such facts is so considerable 

 as to convince nearly all paleontologists and 

 many zoologists. In an excellent summary 

 of the present status of opinion on this sub- 

 ject Cumings' has called attention to illus- 

 trations of recapitulation in each of the 

 classes of invertebrates above the Porifera. 



Against this mass of evidence a mere dog- 

 matic statement has little weight. It is not 

 enough to cry scornfully, " Quelle importance 

 peut-on attribuer a des conclusions basees 

 sur de telles premisses ? " He who would show 

 these premises to be unsound must show 

 Haeckel's law to be invalid by answering the 

 arguments of Hyatt, Cope, Jackson, Beecher, 

 Cumings and many others, and also otherwise 

 account for the great accumulation of evi- 

 dence in favor of the law which appears not 

 only in the works of authors avowedly in 

 favor of the theory but in the facts presented 



' A. Hyatt, ' ' Genesis of the Arietidffi, " p. ix, 

 Smith's Cont. to Knowledge, No. 673, 1889. 



^ E. E. Cumings, ' ' Paleontology and the Ee- 

 capitulation Theory," Proe. Ind. Acad. Sci., 25th 

 anniversary meeting, 1909. 



