450 M. O'Connell — Orthog'enetic Development 



Aet. XXXII. — Ortho genetic Development of the Costce 

 in the Perisphinctince; 1 by Maejoeie O'Connell, Ph.D. 



The word orthogenesis is derived from the Greek 6p06<s y 

 straight, and yeWis, production, and means simply devel- 

 opment or variation in a definite direction. There are 

 at present two different conceptions of the meaning of 

 this term, one being that orthogenesis is a fact made 

 known to us by observation, the other that it is a theory 

 to explain observed facts. A few quotations will illus- 

 trate the divergence in thought in these two fundamental 

 concepts of a single term. 



Eimer, in his paper on 'Orthogenesis and the Impo- 

 tence of Natural Selection,' has made a careful distinc- 

 tion between the fact and the cause of orthogenesis. He 

 was the first to bring the term into general use and it is, 

 therefore, important to know exactly what he meant 

 by it. He says : ' i The translation of definitely directed 

 development (bestimmt gerichtete Entwichlung) into the 

 word 'orthogenesis' was first employed by Wilhelm 

 Haacke in his book Gestaltung und Vererbung in 1893, 

 and as it is very expressive, I have adopted it for my 

 own use." 2 "Orthogenesis," Eimer states, "shows 

 that organisms develop in definite directions without the 

 least regard for utility through purely physiological 

 causes as the result of organic growth." 3 Orthogenesis 

 he defines elsewhere as "the fact that the transmutation 

 of the animal world takes place, not as Darwinism and 

 the advocates, of 'omnipotent natural selection' (Weis- 

 mannian Pseudo-Darwinism) assume, accidentally in 

 numerous and even widely diverse directions, but sys- 

 tematically and conformably to law in only a few direc- 

 tions. ' ' 4 Eimer not only adduced a wealth of illustration 

 in support of his belief in the universality of the law of 

 orthogenesis, but he attempted to formulate the causes 

 and it was here that he came into conflict with the fol- 



1 This paper is based on material in the collections of the Department 

 of Geology and Invertebrate Paleontology of the American Museum of 

 Natural History and was prepared while the author was an assistant in 

 the department, but the researches were carried on and this paper was 

 written outside of official hours. The material was collected in Cuba by 

 Mr. Barnum Brown of the Museum and is described in a forthcoming 

 paper. 



2 Eimer, I. H. Theodor, 1898. Orthogenesis and the Impotence of 

 Natural Selection, p. 19. 



3 Loc. cit., p. 2. 



4 Loc. cit., p. 20. 



