122 EVOLUTION: THE AGES AND TOMORROW 



mission," as Parker called it, and stimuli are carried from 

 cell to cell producing slow reactions. In some of the colonial 

 or semi-multicellular forms, like Vohox, which consist of 

 hundreds of cells embedded in a jelly-like mass, there is a 

 rather rapid cell-to-cell transmission of nervous impulses 

 \^^hich produces remarkable coordination in the locomotor 

 activity of these organisms. The first true nervous cell ap- 

 pears at about the level of the coelenterates (jelly fishes, sea 

 anemones, and hydra) where it is incorporated in special 

 sense organs and in muscle. The cell and its arrangement is 

 primitive, and the nervous transmission is through a net- 

 work of diffuse and directionless nerve fibers. Stimuli travel 

 in all directions from any one source, a situation which suits 

 the peculiar and rather simple locomotor activity of jelly 

 fishes, but which would produce nothing but chaotic con- 

 vulsions in any higher animal. There is no true centraliza- 

 tion and nothing like the real beginnings of a brain, but the 

 three essential behavior tissues are present: some cells are 

 specialized for detection of stimuli (light, chemical sub- 

 stances, contact, and so on); some are connected to muscle 

 fibers; and some are the true nerve cells and specialize in 

 efficient conduction to, and organize the activity of, all parts 

 of the body. 



Psychologists who have studied the behavior of coelen- 

 terates find them capable of intelligent responses in the sense 

 of an ability to learn. In the 1951 Handbook of Experi- 

 viejital Psychology, a phylogenetic comparison is summa- 

 rized by H. W. Nissen in which he reports the literature as 

 showing a definite learning capacity in the coelenterates. 

 Pieces of paper were placed on some of the tentacles of sea 

 anemones at daily intervals. The animal would at first grasp 

 the paper and bring it to the mouth where it was swallowed, 

 only later to be rejected. After some few trials the paper 

 was not swallowed, and finally the animal would not even 

 grasp the paper in the first place. After some of the tentacles 

 were trained, the untrained tentacles learned more quickly 



