ECOLOGICAL BACKGROUND AND GROWTH BEFORE 1900 



23 



ages on the "Beagle" and the "Rattlesnake," 

 respectively, exerted strong formative influ- 

 ences upon Charles Darwin and T. H. Hux- 

 ley. Many others have had and continue 

 to have their biological thinking channel- 

 ized and intensified by direct observations 

 on the unaccustomed richness of the eco- 

 logical relationships of plant and animal 

 life of the tropics. 



Milne-Edwards (1857) pubhshed a basic 

 contribution on the processes and organs 

 of respiration in animals. In the next two 

 decades, knowledge of the respiration of 

 aquatic animals was advanced decidedly. 

 In this connection, the work of Bert (1870) 

 and Fritz Miiller was available to Semper. 



Bert (1878) emphasized the interrela- 

 tions between barometric pressure and oxy- 

 gen tension. He knew that the eflFect of 

 lowered or increased atmospheric pressures 

 can be obviated by adjusting the final par- 

 tial pressure of oxygen to that to which 

 the animals are acclimated. Fairly large 

 changes from this pressure are normally 

 harmful. Animals with closed, or nearly 

 closed, internal reservoirs of air show me- 

 chanical eflFects from variations such as 

 might be expected from a general knowl- 

 edge of the phvsical principles involved. 

 Bert also knew about the internal release 

 of nitrogen in decompression. It is an item 

 of more than passing interest that a trans- 

 lation of this thousand-page monograph was 

 published in 1943. 



The importance of the evaporating power 

 of the air on animal distribution was well 

 recognized by 1880. There was also a con- 

 siderable body of knowledge concerning 

 mechanisms that allow gill-breathing ani- 

 mals such as crabs, and fishes such as Peri- 

 ophthalmus, to invade the land, sometimes 

 for extended periods of time. Forel's ob- 

 servations on the reinvasion of deep water 

 by the air-breathing Lymnaeidae were also 

 on record. 



The ecologically-minded zoologist of the 

 1870's was also interested in the influence 

 of water in motion upon such matters as 

 the clinging power of mollusks, erosion of 

 shells, form of coral reefs and the relation 

 of currents of water (or air) to the distri- 

 bution of species. The importance of the 

 substrate was recognized, and many natural 

 history aspects of reciprocal reactions of 

 living organisms upon each other were 

 given much attention, especially the rela- 

 tions of sexes and various sorts of symbi- 



osis, including commensahsm, mutualism, 

 and parasitism. Semper was also quite 

 aware of the relationship between his data 

 and the Darwinian theory of evolution. In 

 this he seems to have been in advance of 

 some of the more self-conscious ecologists 

 who followed him. 



RESPONSE PHYSIOLOGY* 



Ecological aspects of response physiology 

 are mainly concerned with phases of be- 

 havior. The attention centers on the behav- 

 ior of animals, since their reactions are 

 much more marked than are those of plants. 

 The responses of organisms are important 

 in ecology because they are frequently ini- 

 tiated primarily by the environment and 

 in turn react upon it. Since vocalization, 

 which may be easily and sometimes pre- 

 cisely interpretable in communication from 

 man to man, is not equally revealing among 

 other animals, the most sensitive clue to the 

 eflFect being produced by an environment 

 is frequently gained from the response 

 physiology of the reacting animals. 



The history of this aspect of ecologv also 

 traces back to Aristotle, who recorded a 

 somewhat systematic account of the be- 

 ha\ior of many sorts of organisms. His ob- 

 sers'ations, despite their defects, exerted 

 an influence in this phase of developing 

 ecological knowledge which, with the pos- 

 sible exception of that of Reaumur (1683- 

 1757), was hardly equalled before the time 

 of Charles Darwin. 



Wallace in Malaya and South America, 

 Hudson in the Argentine, Bates on the 

 Amazon, Belt in Nicaragua, and many 

 others made sturdy contributions to our 

 knowledge of the behavior of little-known 

 animals, which they observed on expedi- 

 tions or in out-of-the-wav places. Espinas' 

 consideration of social animals (1877) was 

 based on records or observations concern- 

 ing native as well as exotic forms. Brehm's 

 Tierlehen in its successive editions was the 

 outstanding natural history of the period 

 as BuflFon's Hisfoire Naturelle had been a 

 centurv earlier. Romanes made good obser- 

 vations, not onlv on the behavior of Cehiis 

 monkevs, but also on jellyfishes, starfishes 

 and sea urchins. Preyer experimented on 



• The interested student is referred to 

 Holmes (1916) and Warden, Jenkins, and 

 Warner (1935) for the history of the study of 

 animal behavior. 



