168 NATURE SKETCHES IN TEMPERATE AMERICA 



takes place in a much more flexible and less 'directly machine-like 

 way, by the method of trial and error. This method involves 

 many of the fundamental qualities which we find in the behavior 

 of higher animals, yet with the simplest possible basis in ways 

 of action; a great portion of the behavior consisting often of 

 but one or two definite movements — movements that are 

 stereotyped when considered by themselves, but not stereotyped 

 in their relation to the environment.* 



To account for the behavior of the greater number of ani- 

 mals from the protozoa up to the insects, Bobn ^ has recently 

 expressed his opinion that their actions may be accounted for 

 partly by mechanical reflexes, partly by certain vital rhythms, 

 and by sensation, which may be described as differential 

 sensibility. With the development of the special sense organs, 

 especially the eyes, there is a coincident development of a 

 certain degree of mentality. It is a complicated functioning 

 of the nervous system and not of a kind that recognizes a 

 dual conception of mind and body. In the behavior of these 

 animals, there is exercised association of sensations in addition 

 to tropismic responses. Following upon this stage of life in 

 the animals above the insects, or vertebrates, the dawii of 

 intelligence appears. The association of sensations now dom- 

 inates over the lower mechanical reflexes and tropisms. 



The special sense organs in the lower vertebrate animals 

 are, comparatively considered, of the saftie kind as our own, 

 though varying in the grade of perception of vibrations of 

 light and sound. It is in dealing with the invertebrate 

 animals that we may have difficulty in understanding their 

 impressions of the world about them, especially inasmuch as 

 the disposition of their sense organs, so far as demonstrated, 

 is often in very difl^erent parts of the body as compared to that 

 of the vertebrates. It will do here to cite the case of the organs 

 of olfaction, or smell, in the insects. They are situated in the 

 joints of the antennae. Again we have the organ of hearing 

 situated in the basal joint of the abdomen in the grasshopper. 



' Those interested in animal behavior will find their time most interestingly 

 spent by keeping insects and other animals indoors to study. The plant 

 house furnishes a desirable place to rear or breed them. 



^"La Naissance de V Intelligence." 



