FIRST FOUR DECADES OF THE TWENTIETH CENTURY 



45 



if of subtle character, could control an ani- 

 mal's orientation and pattern of movement. 

 Also, it had a si2;nificant influence on the 

 ihinkinci; of biologists generally. The first 

 edition of The Animal Mind by Washburn 

 (1908), to be followed by several further 

 editions, laid certain foundations for the 

 study of animal behavior. 



There was much writing during the dec- 

 ade on the behavior of a single species, 

 "^his IS well typified by the study by Ray- 

 mond Pearl, whose excellent and original 

 monograph on the behavior of Planaria 

 summarized the state of things at that time 

 iT- these words (1903. p. 511) : 



"... Aside from the researches of a few 

 investigators on a small number of forms, we 

 have little detailed knowledge of the behaviour 

 of lower organisms. It is coming to be realised, 

 too, that knowledge of what an animal does is 

 just as important in the general study of life 

 phenomena as a knowledge of how it is con- 

 structed, or how it develops." 



There are also some writings on social 

 behavior. Wheeler's classical book on "Ants" 

 appeared in 1910 (reprinted. 1926) and, 

 through its emphasis on ant behavior, did 

 much to stimulate behavior studies on the 

 social insects and to provoke comparisons, 

 sometimes invidious, between insect and 

 human responses. A paper by Craig (1908) 

 on pigeons suggested that the vocalization 

 of these birds had some function in the 

 social control of the flock. 



The field of developmental physiology 

 was equally active. It also received impetus 

 from Davenport's summary. Mention of sev- 

 eral studies wall suffice to show the nature 

 of the research of this period. Among 

 others, the works of Bachmetjew (1901, 

 1901a, 1907) stand out. He not only sum- 

 marized a wealth of literature, but pre- 

 sented as well many original observations 

 and interpretations. Bachmetjew was con- 

 cerned largely with the effect of light and 

 temperature on various phases of the de- 

 velopment and distribution of insects. Prob- 

 ably one of his more significant contribu- 

 tions was his summary of the eflFect of low 

 temperature on insect protoplasm. Chap- 

 man (1931, p. 61) states this in concise 

 form as follows: "The insect may be 

 cooled below the freezing point without 

 being injured. The freezing point may be 

 past, and the insect may exist in an under- 

 cooled condition. When it does freeze, the 



heat of crystallization will be equal to the 

 undercooling temperature, and the body 

 temperature will rebound to the freezing 

 point. Cooling will again proceed; and 

 when the insect reaches the undercooling 

 point the second time, death follows, ac- 

 cording to Bachmet Jew's conception." More 

 modem views do not completely agree 

 with this interpretation, but in 1901 it was 

 an important pronouncement with cogent 

 ecological implications. Bachmetjew also 

 discoursed on light and temperature in rela- 

 tion to zoogeography. 



Branching ofi^ from developmental physi- 

 ology is a phase of research that some ecol- 

 ogists designate "toleration physiology" or 

 "toleration ecoloey." In such work the con- 

 cern lies with the limits of toleration for 

 organisms exposed to various intensities of 

 environmental factors or combinations of 

 thesf factors. During the decade 1900 to 

 19 K'' there were some studies of this type, 

 and an example or so mav be cited. Pack- 

 ard (1905, p. 33) published a paper on 

 the efi^ect of low oxygen tension on sur- 

 vival of certain marine fishes and inverte- 

 brates of the Woods Hole (Massachusetts) 

 area. In addition, he showed that if the 

 blood alkalinity of Ftinduhis heteroclitus 

 was increased, there was a corresponding 

 increase in the tolerance of the fish to lack 

 of oxygen. Contrariwise, increasing the 

 acidity of the blood made the fish less tol- 

 erant of low oxygen tensions. Bachmetjew 

 (1907) recognized this general problem for 

 insects and published a list of extremes of 

 temperature that various insects have been 

 known to tolerate. Another such list ap- 

 peared in Davenport (1908). 



Natural history has always been inextri- 

 cably interwoven with ecology. In fact, 

 ecology has been called "scientific natural 

 history." Much of the content of ecology 

 is natural history, and the ecologist usually 

 experiences a certain pleasure in observing 

 and recording the "history of nature." But 

 natural history is not a closely definable 

 entity. It may range from superficial and 

 even misleading nature study, to excellent, 

 precise investigation. Earlier in this section 

 we saw how this phase of ecology contrib- 

 uted to the rise of the science. 



During the decade 1900 to 1910 ex- 

 amples can be chosen that rrm the gamut 

 of type. There were books such as that of 

 Chapman (1900), designed largely for the 

 nature student and amateur. It is hard to 



