22 



THE HISTORY OF ECOLOGY 



Those of Dallinger (1887), still cited ex- 

 tensively, covered several years, during 

 vvlrich time he slowly acchmated a popula- 

 tion of flagellates to heat. At the beginning 

 they started to die if raised to 23^ C; 

 finally they were Hving at 70° C. At this 

 point the experiment was terminated by 

 an accident; neither the nature of this 

 event nor DaUinger's emotions at the time 

 are revealed in tiie original reports. 



Davenport's conclusions, based on knowl- 

 edge available in 1896, have a distinctly 

 modern sound. In general terms, not in ex- 

 act quotation, he says (1897, p. 277) 

 that when dynamic conditions vary quan- 

 titatively, a quantitative variation in metab- 

 ohsm will follow such that metabohsm be- 

 gins to slow down as limiting conditions 

 are approached. And finally: "A vital phe- 

 nomenon occurring in a given protoplasmic 

 mass can be reproduced only when the 

 dynamical conditions are reproduced, and 

 the structural hmiting conditions are in no 

 wise closely approached." 



Semper's earher Animal Life (1881) is 

 less fully documented and hence is some- 

 what less helpful in strict chronology. His 

 book has the distinct advantage of being 

 written from much more nearly the modern 

 ecological point of view than was Daven- 

 port's. A brief review of some of his points 

 will increase our knowledge of, and respect 

 for, the ecological information available at 

 the close of the 1870's. 



Semper knew of monophagy in the strict 

 modern sense among both carnivores and 

 herbivores. He also knew that monophagy 

 is often closely connected with the occur- 

 rence of special organs or structural rela- 

 tions, or with special adjustments in the 

 Life history. He clearly foreshadowed the 

 modern conception of "key-industry" ani- 

 mals, and he worked out in principle what 

 has come to be called the "pyramid of num- 

 bers" (p. 52). 



Protective color changes in animals have 

 long been a matter of interest. Semper 

 (p. 91) reports that Stark in 1830 recorded 

 observations on color changes in several 

 different kinds of fishes; Shaw in 1838 was 

 perhaps the first to conclude that fishes 

 that can change color are apparently pro- 

 tected thereby from predators. Lister 

 (1858) found by experimentation that a 

 connection exists between eyes and chroma- 

 tophores in frogs, a relationship later inde- 

 pendently confirmed by Pouchet (1876), 



who experimentally demonstrated that the 

 connection existed through the sympathetic 

 nervous system. Except in the growth of 

 detailed knowledge and the formulation of 

 the ratio hypothesis to explain background 

 matcliing (Keeble and Gamble, 1904), the 

 next important advance in the matter of 

 knowledge about cliiomatophore activity 

 came with the relatively recent insight into 

 the role of hormones and of neural hmnors 

 in the ecological relations of animals ca- 

 pable of color change to fit their environ- 

 ment. 



Semper strongly doubted the significance 

 of the classification of animals according 

 to the temperature zones in which they five 

 in "fortuitous community." He thought that 

 the well-being of animals that five in asso- 

 ciation depends far more essentially on the 

 variations and extremes of temperature than 

 on the absolute degree of heat to which 

 they may be simultaneously exposed at any 

 given time. Hence he found the cUstinction 

 that Mobius had made between stenother 

 mal and eurythermal to be as important as 

 we now hold it to be. 



In a much more speciaUzed field, Semper 

 anticipated the modern human preoccupa- 

 tion with "Lebensraum" and extended the 

 earher experiments of Hogg (1854) to 

 show that the fresh-water isopod Asellus 

 and the pond snail Lijmnaea would be 

 stunted if grown in too small a volume of 

 water. He failed to find an adequate ex- 

 planation experimentally and invented the 

 hypothesis of the presence of an unknown, 

 but necessary, substance, which was present 

 in the water, probably in a minute quan- 

 tity. Since a certain quantity would be 

 needed, it follows that below a minimum 

 volume, growth would be retarded. While 

 we know much more now than when 

 Semper was experimenting, this problem is 

 still essentially unsolved; the present knowl- 

 edge about the importance of vitamins and 

 other trace substances lends significance to 

 Semper's guess. 



Semper was a morphologist, uninterested 

 in ecological relations before he went to 

 the Philippines on his great expedition. 

 Close contact with coral reefs in particular, 

 and with the wealth of life in general, ap- 

 pears to have changed his approach to bi- 

 ology. This is a dramatic, though not an 

 isolated, example. The effect of similar per- 

 sonal experience with varied and, to them, 

 exotic aspects of nature, during their voy- 



