THE CAMBRIAN PERIOD. 291 



were specially adapted to defend them against the trilobites, as we 

 should expect them to be if evolved for this special purpose. 



While final conclusions can scarcely be reached by such studies, 

 they lend interest to the study of the parts which are chiefly fossilized 

 and throw a little light on the life of these early inhabitants of the 

 globe. 



Sociological development. — If sociology be defined as the relation- 

 ship of one living thing to others, the relations of attack and defense 

 may be said to constitute the militant phase of the sociological develop- 

 ment of the Cambrian times. These beginnings ,,of animal sociology 

 possess no small interest and importance, however crude they may 

 seem to be, if we entertain the doctrine of evolution in its broader 

 phases which embrace mental as well as physical evolution. The 

 adjustment of the organisms to one another and the development 

 of qualities, physical and mental, suited to such adjustment, is a sub- 

 ject applicable to all the ages in which conscious life prevailed, and 

 the simple lessons of its crude beginning may not be less instructive 

 than the more intricate ones of the late stages. The early evidence, 

 to be sure, is imperfect, and the interpretation is by no means sure, 

 but it nevertheless merits attention. 



The shells of trilobites are sometimes found together in large num- 

 bers. Occasionally they are closely packed, " spoon-fashion/' Not 

 unlikely these may be the molted shells, for the habit of molting 

 had been acquired even at this time. Possibly the assembling of 

 the shells may be the work of currents or similar inorganic agencies, 

 but the suggestion that the trilobites were gregarious, either habitually 

 or seasonally, may be entertained. Obscure and uncertain as these 

 and similar suggestions may be, we shall not have followed the his- 

 tory of life development far before the evidences of social relations 

 will be distinct and unmistakable. 



Mental development. — The wars of the Cambrian inhabitants, 

 implied by their weapons of offense and defense, can scarcely have 

 been unaccompanied by some notable measure of mental develop- 

 ment, however the nature of such development may be interpreted. 

 That the trilobites sought their food or pursued their prey by sight, 

 and were guided by touch, their eyes and their antennae imply, and 

 it is difficult to conceive of these actions without the mental processes 

 that usually attended on pursuit and capture. The control of so com,- 



