260 TJniversity of California Publications in Zoology [Vol. ii 



for several successive times. The path along the reflex ring to 

 the particular effectors involved is made more permeable. Sher- 

 rington (1911) says: "The overflow of reflex action into chan- 

 nels belonging primarily to other reflex-arcs than that under 

 stimulation leads to the production by the single stimulus of a 

 wide, compound reflex which is tantamount in effect to a simul- 

 taneous combination of several allied reflexes." 



Fig. 6. — Diagrammatic representation of a nerve ring. Adapted from 

 von UexkuU (1905). 



With a nerve ring consisting of the connections for the few 

 distinct elements of these apparently very complex movements, 

 I believe a satisfactory explanation of the modus operandi is 

 afforded. These elements would be such as a turn to the right, 

 a turn to the left, a connecting link with a ring producing the 

 looping response, and a similar one with the swimming reflexes. 

 Such a view is in accord with the current nerve physiology, and 

 makes relatively simple what at first sight appears markedly 

 complex. 



States of excitement indicate changes in the nerve centers 

 as well as in the muscular tissues, and these changes, though 

 ever so slight, may produce widely different responses to the 

 same stimulus. Thus we have accounted for, on a satisfactory 

 basis, the different reactions to the same stimulus in the various 

 physiological states or states of excitement in the lech. 



