ANIMAL BEHAVIOR. 307 



general instinct of preying, which is doubtless coeval with ani- 

 mal organization. The cannibalism of our protozoan ancestors 

 was the starting-point, and their carnal propensities were not 

 acquired by the aid of intelligence, but given in the fundamental 

 properties of protoplasm. The stronger ate the weaker, and 

 made themselves stronger and more prolific by so doing. The 

 promise of the whole animal world was contained in the act. 

 The constitutional disposition to feed, with variable foods avail- 

 able, would give occasion for different appetites and various 

 modes of getting outside of palatable victims. In primitive 

 organisms multiplying by simple fission, structural modifica- 

 tions acquired during the lifetime of the individual would be 

 carried right on from generation to generation, and hence the 

 structural foundations for a whole animal world such as we now 

 see could be laid in a relatively short period as compared with 

 the time necessary to advance organization in forms limited to 

 reproduction by germs. In fact, these fundamentals could all 

 be established within the realm of the unicellular protozoa. 

 Nucleus and cell-body, inner and outer layers, nerve-muscle 

 elements, sensory and locomotor organs, mouth and stomach, 

 respiratory and excretory mechanisms, reproductive elements, 

 anticipating embryological development from germs — all these 

 essentials of higher organization are presented in the pro- 

 tozoan. 



The organic bases furnished in the protozoan world might be 

 passed directly on to the first metazoa, or they might be reac- 

 quired in essentially the same manner as before, and in a not 

 much longer period, as reproduction by fission would still be a 

 condition favoring rapid organo-genesis. 



To try to fill up the gaps between the protozoan and Nectii- 

 rits would lead us too far into the field of speculation, and 

 would not contribute much to a grasp of the problem. We 

 have to content ourselves with general facts and principles and 

 probabilities drawn therefrom. It is enough for present pur- 

 poses to know that the roots of the instinct organization we are 

 considering run clear back to the beginnings of organo-genesis, 

 and that they are natural products of the properties of living 

 protoplasm. We start with known properties and get to known 



