496 
ZOOLOGY: CROZIER AND AREY 
Furthermore, the fact that the intrabronchial injection of a minimum 
culture proved fatal only when the injection was made ten days after 
the section of one vagus and the further consideration of the fact that it 
takes about ten days for the degeneration of vasodilators lend support to 
the assumption that it is the degeneration of the vasodilators which is 
responsible for the fatal results observed in our experiments. 
ON THE ETHOLOGY OF CHITON TUBERCULATUS' 
By W. J. Crozier and L. B. Arey 
University of Illinois and Northwestern University 
Communicated by E. L. Mark, September 5, 1919 
Chitons of the species C. tuherculatus Linn, are an important element 
in the shore-fauna of the Bermuda Islands. Their large size, their 
abundance, and the diversity of the habitats which they occupy within 
the tidal zone, make them animals appropriate for a variety of investi- 
gational purposes — notably for study of the relations found among the 
features of local habitats, on the one hand, and, on the other, certain 
definite sensory and other modifications of these animals which develop 
with the advancing age of a chiton. The organization of the Placophora, 
probably primitive with reference to that of other molluscs, makes it 
important also to obtain physiological evidence as to the characteristics 
of the nervous system in these animals. On the structural side it is well 
known that the chiton central nervous system is in the form of strands, 
containing perikarya throughout their length, but with no concentrations 
of these cells into distinct ganglionic enlargements. 
We find in Chiton tuherculatus decided indications of but a, relatively 
incipient degree of nervous centraKzation. The autonomy of the sev- 
eral portions of the body, or of the parts into which it may be artificially 
separated, is conspicuous. At the sides of the body, the parts (girdle, 
ctenidia, etc.) innervated by the pallial strands are pronouncedly homo- 
lateral in their responses. The coordinating mechanism for the produc- 
tion of pedal locomotor waves is locally contained. The absence of 
strong anterior nervous centraKzation is nicely indicated by the exhibi- 
tion of backward creeping (especially in Ischnochiton) under proper 
conditions of stimulation by light. 
Of the several kinds of sensory receptors which we have distinguished 
in Chiton tuherculatus, the nervous elements in the shell tegmenta, now 
for the first time proved to be photosensitive, are perhaps the most 
