THE NERVOUS SYSTEM OF AMPHIBIA 201 



antagonism between reflexes after the manner of the mammalian 

 reflex arc. 



In my paper upon Diemyctylus ('09) attention was called to 

 the secondary movements which occur in the behavior of these 

 embryos, that is to say, movements that frequently occur im- 

 mediately after the initial response or before it is completed. 

 These movements might be accounted for upon the hypothesis 

 that the motor or associative cells act rhythmically to a single 

 stimulus, only for the fact that the secondary movement some- 

 times exceeds the initial movement in extent. Although there 

 may be a tendency for these cells to act in rhythm, there must be 

 something besides the rhythmic activity to account for the accel- 

 eration of movement. In the light of the anatomical and physio- 

 logical demonstration of a proprioceptive field of stimulation it 

 is more reasonable to suppose that stimuli from this field, through 

 imperfect alliance with stimuli from the cutaneous field, arouse 

 the secondary movements. We may recognize in these movements, 

 therefore, the phenomena of alliance between reflexes. The 

 movements, in and of themselves, have the characteristics of 

 the reflex after-discharge of the mammalian reflex arc, and, indeed, 

 regardless of the above interpretation of their immediate cause, 

 they may be perfectly analogous to the reflex after-discharge, 

 since the latter response of the mammalian reflex arc may involve 

 both the rhythmic action of neurones and excitation from the 

 proprioceptive field. 



The anatomical part of the paper brought out the fact that 

 a single giant ganglion cell may innervate both skin and muscle. 

 Some of these cells are apparently distributed exclusively to 

 the skin; others may be distributed exclusively to the muscles; 

 but some certainly go both to skin and muscle. In the consider- 

 ation of the interaction of stimuli from the skin on the one hand 

 and from the muscles on the other, it is necessary, therefore, to 

 assume that there is no physiological differentiation between the 

 stimuli from the different sources. Exteroceptive and proprio- 

 ceptive stimuli might become allied, or the one reinforce the 

 other, within one and the same neurone. 



