572 



SCIENCE 



[N. S. Vol. II. No. 44. 



showing that the problem of species and 

 their A'ariations may be compared to the 

 examination of tlie positions of equilibrium 

 of a point placed on a resisting surface and 

 submitted to the action of a force which is 

 a function of the coordinates of the point. 

 The discussion of this problem of mechanics, 

 translated into zoological language, leads to 

 the following conclusions : That in a given 

 fauna in a given environment there is but a 

 limited number of possible species, and that 

 the passage of the initial forms to the de- 

 finitive forms will be made yerj^ rapidly. 

 This explains the small probabilitj' of find- 

 ing remains of the transitional forms. The 

 same applies to the transition of one fauna 

 to another under the action of a changed 

 environment. 



Prof Eimer (Tiibingen) spoke on defi- 

 nitely directed development (orthogen- 

 esis) and the impotence of Darwin's selec- 

 tion in the formation of species ; also upon 

 the development of species and af&uities of 

 the swallow-tailed butterflies. The speak- 

 er's works, which in part have been pub- 

 lished for years, especially those on the 

 markings of animals, show that definitely 

 directed development is an unquestionable 

 fact and his continued investigations every- 

 where confirm this. Variation always takes 

 place in a few quite distinct directions, 

 progressively, or sometimes (Foraminifera) 

 retrogressively, new?' ' oseillatLagly.' Utility 

 plays no part, either in the minimal be- 

 ginnings or in the further development. 

 Transformation is to be referred to the in- 

 fluence of the environment upon a given 

 constitution. Selection can create nothing 

 new, but what is developed may become 

 useful and be selected. The separation 

 into species of the chain of organisms thus 

 formed occurs chiefly through arrest at 

 definite stages of development (Genepis- 

 tasis) as well as by saltatory development 

 (Halmatogenesis) and by hindrance of fer- 

 tilization (Kyesomechania). Even the 



origin of apparently mimicking forms is to 

 be explained by definite directioas of devel- 

 opment (independent similarity of develop- 

 ment, Homceogenesis). Only thus, not by 

 selection, is the origin of mimicry made in- 

 telligible. The speaker employed, as evi- 

 dence for his views, figures of the Papili- 

 onidce, from which, as he said, the laws of 

 , development and of the formation of species' 

 may be read as from the letters of a book. 

 The fact of the definitely directed develop- 

 ment of non-useful characters completely 

 refutes the lately propounded ' germinal 

 selection.' Speculation may have its place 

 in natural science, but it must not ignore 

 facts previously established. 



Dr. E. Bowdler Sharpe presented a paper 

 on the geographical distribution of the 

 birds of prey, and M. F. Mocquard (Paris) 

 one upon some new reptiles and amphibians 

 from the upper Congo. 



Dr. T. Schmitt made a communication on 

 the principles followed in preparing the 

 new edition of the Scandinavian Fishes. 



In the paper of M. Forrest, presented by 

 the Baron d'Hamonville, upon the ostrich, 

 egrets and bu-ds of paradise, the principal 

 points were: (1) Reintroduction of the os- 

 trich into North Africa. (2) To have 

 measures for the protection of the egrets 

 univei'sally adopted. (3) To obtain pro- 

 tection for the birds of i^aradise. 



Prof. W. Leche (Stockholm) gave an 

 outline of his investigations upon the devel- 

 opment of the dental sj^stem in mammals, 

 emphasizing the general considerations 

 which are to be regarded in this question. 

 He dwelt upon the fact that the serial ap- 

 pearance of the teeth had been only gradu- 

 ally acquired and also that there are no im- 

 passable barriers between the diflferent den- 

 titions. He pointed out the occurrence of 

 at least four dentitions in the mammals and 

 made some statements concerning the gen- 

 esis of these. 



Prof. Semon (Jena) spoke on the fos- 



