author's abstract of this paper issued 
by the bibliographic service, february 7 
ON THE NATURAL HISTORY OF ONCHIDIUMi 
LESLIE B. AREY and W. J. CROZIER 
Northwestern University Medical School and Hull Zoological Laboratory, The 
University of Chicago 
CONTENTS 
Introduction 443 
Occurrence; 'homing' activities; coloration; repugnatorial glands 445 
Sensor}' responses 459 
1. Mechanical excitation 459 
2. Photic excitation 464 
3. Thermal excitation 474 
4. Chemical excitation 476 
On the analysis of the homing behavior 479 
Discussion 489 
1 . Origin of Onchidium 489 
2. Heliotropism and the analysis of conduct 489 
3. On the nature of heliotropic inhibition and reversal 491 
4. The question of persisting rhythms of behavior 493 
5. The comparative physiology of homing movements 493 
Summary 497 
Literature cited 499 
INTRODUCTION 
Onchidium (Onchidella) floridanum Dall belongs to a group 
of naked pulmonates (Pelseneer, '01, p. 21) which, after the long 
discussion concerning the obscure morphology of their respira- 
tory apparatus (cf. Joyeux-Laffuie, '82; Bergh, '95; v. Wissel, 
'98), have been chiefly remarkable for their littoral marine 
habitat, and, more conspicuously, for the eyes— of a structural 
type unique among gastropods (Semper, '77; Stantschinsky, 
'07; Hirasaka,^ '12) — developed by some of them upon their 
' Contributions from the Bermuda Biological Station for Research, no. 126. 
^ We are indebted to Mr. T. Minoura, of the zoological department, L^niver- 
sit}^ of Chicago, for a knowledge of Hirasaka's paper, and for his kind translation 
of essential portions of its contents, as well as for his translation of Fujita's ('97) 
account of the respiration of the Japanese Onchidium. 
443 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 32, NO. 3 
