ANIMAL BEHAVIOR — WELLS 427 



ample ; 5 this facilitates a physiological approach. No doubt there are 

 plenty of other subjects at least as favorable to be found among the 

 invertebrates. The situation is vastly more complicated in a bird or a 

 mammal. Its activities are harder to record, its body is less amenable 

 to operation, and because of its restless habits and highly developed 

 sense organs its behavior is interfered with by the environment more 

 continually and in more varied ways than is that of a worm. Much of 

 the underlying inherent structure of its behavior can be seen, but the 

 experimental investigation of the timing mechanisms would be very 

 difficult. 



I cannot resist the temptation of adding a wild little fantasy about 

 communication. 



If you lie in a deck chair in your garden with your eyes shut and 

 listen to a bird — and if you know your bird as well as Dr. Sauer 

 knows his whitethroat — you can tell what is passing through its mind 

 from its calls and from variations in the timing and structure of its 

 song, and you can see in your own mind's eye nearly everything it does. 

 Similarly, if you make a worm write its water currents on paper, and 

 if you know your worm, you can tell from the patterns it traces what 

 it is doing at any time. The two have this in common : in each case 

 you study one aspect only of the animal's activities, but in each case 

 the behavior of the animal is so closely integrated that nearly every- 

 thing it does is reflected in that one. They differ in this: the voice 

 of the bird is a method of communication ; another bird can hear what 

 the first one says. The usual effect of bird communication is to bring 

 both into the same mood. Such moods as restlessness, alarm, or lazy 

 contentment can spread by this means through a flock of birds so that 

 all are in the same condition and prepared to act in the same way — 

 this has been described by Professor Lorenz in jackdaws and geese, by 

 Dr. Tinbergen in gulls, by Dr. Hinde in great tits, and by many 

 others too. But take your bird and isolate it in a soundproof room 

 and it still continues to call and sing. The parallel with the worm is 

 now very close indeed, for in both cases you get the performance of 

 intricate spontaneous rhythms, and in both you get changes of mood. 

 Perhaps it is only 99 percent fantastic to say that the worm, though it 

 is a dumb animal and has not yet invented a way of communicating 



5 Sabella generally whips its head back into its tube at the approach of a preda- 

 tor, such as a fish ; but sometimes it fails to do so fast enough, and loses not 

 only its head but also several segments from the front end of the body. It then 

 grows a new head, which can be distinguished by minor anatomical characters 

 from the old, and Professor N. J. Berrill has written : "In nature it would 

 seem that about half the Sabella population suffers such mutilation at one time 

 or another." I found that the normal activity-time patterns (as registered by 

 the water currents) are hardly altered, if at all, by the loss of the front end 

 of the body. 



