360 



SCIENCE. 



[N. S. Vol. III. No. 62. 



1st period. The oldest attempts of A. Wag- 

 ner, L. Agassiz, Dana and Schmarda. 



2d period. To A. Agassiz and Wallace. The 

 period of the discussion about the number of 

 zoogeographical regions, and the first attempt 

 to lay a scientific basis for zoogeography. 



3d period. From Wallace to Heilprin, Troues- 

 sart and Doderlein. The period of the special 

 researches on single groups of animals, with 

 more or less considerable acceptance of the 

 principles of Wallace ; full treatment of single 

 groups. 



At the end of the chapter Ortmann refers to a 

 very important paper of Pfeflfer : Versuch iiber 

 die erdgeschichtliche Entwicklung der jetzigen 

 Verbreitungsverhiiltnisse unserer Thierwelt, 

 Hamburg, 1891, which he considers as possibly 

 the best ever published on zoogeography ; he 

 also refers to the new work of J. Walther. 

 Einleitung in die Geologie als historische Wis- 

 senschaft I. Theil. Bionomie des Meeres. Beo- 

 bachtungen iiber die marinen Lebensbezirke 

 und Existenzbedingungen. Jena. 1893. 



The second chapter treats of the most im- 

 portant physical life conditions, the life regions 

 and the facies (' Bionomy'). Ortman distin- 

 guishes the following life regions. 



1. The terrestrial region of Terrestrial (con- 

 tinental). 



2. The fresh-water region or Fluvial. 



3. The literal region or Litoral. 



4. The pelagic region or Pelagial. 



5. The abyssal region or Abyssal. 



After this the adaptations of the organisms to 

 the life regions are discussed. The organisms 

 are divided into two groups according to their 

 dependence on the bottom* (Substrat). Ani- 

 mals which are dependent on the bottom and 

 are unable to free themselves from it constitute 

 the Benthos (Haeckel); animals which are not 

 dependent on the bottom, those which during 

 their lifetime never need to come into connec- 

 tion with the coast or the bottom of the ocean 

 constitute the Plankton (Haeckel). Among the 

 benthonic animals three groups are distinguished 



* Brooks, William K. Salpa in its Eelation to the 

 Evolution of Life. Stud. Biol. Labor. Johns Hopkins 

 Uni., Vol. v., No. 3, May, 1893. (This paper was 

 unknown to the author. ) 



according to their more or less intimate connec- 

 tion with the bottom; first, sessil benthos, at- 

 tached to the bottom, receiving food from out- 

 side ; second, vagile benthos, creeping and run- 

 ning on the bottom to obtain food; and third, 

 nectonic benthos, able to swim, able to leave the 

 bottom at times, but always forced to return 

 to it. The nectonic condition forms the transi- 

 tion to the typical plankton, which is independent 

 of the bottom. The three groups of benthos are 

 characteristic for the litoral and abyssal. The 

 true plankton is characteristic for the pelagial. 



The condition of the facies is of course of the 

 highest importance for the organism. Ortmann 

 distinguishes primary and secondary facies, the 

 first is formed only by anorganic, the second 

 also by organic material; but of course there 

 are many combinations of the two. Each life 

 region, however, with the exception of the open 

 sea, has its special facies. The basis of the 

 continental facies is the geological structure of 

 the continents. Of great importance are the 

 physiographic differentiations of the land. 



In the fluviatile life regions the conditions 

 are similar, but here much depends on the dif- 

 ferent nature of the medium; that is, the nature 

 of the course of the water — lakes, rivers, etc. 



The litoral, through its nunierous relations to 

 the land, and its frequent dependence on the 

 nature of the latter, shows very numerous dif- 

 ferences in its facies. 



The facies of the abyssal consists of the small- 

 est disintegrated products of minerals and 

 rocks, accompanied by remains of terrestrial 

 and marine organisms. 



The pelagial has no facies. Peculiarities are 

 produced, however, in the sargassum-masses. 



The third chapter is headed: Distribution of 

 Animals. Increase and prevention of distribution. 

 Means of Distribution. It begins with the defi- 

 nition of the principle of separation and migra- 

 tion, which is of the greatest importance for 

 the understanding of the processes connected 

 with the origin of species and which is insepa- 

 rable from zoogeography. This important prin- 

 ciple was especially studied by Moriz Wagner, 

 but, as Ortmann very properly states, has been 

 misunderstood by many authors, or not ac- 

 corded its full value. In order to estimate cor- 

 rectly the value of this principle, and in order 



