168 



bulletin: museum of compaeatiye zoology. 



C. Theoretical Considerations 215 



1. Comparison of tlie Otocyst with the Vertebrate Ear 215 



2. Neurou Theory 217 



Part n. — Physiology 



218 



A. Historical Survey 



B. Experiments and Observations 



I. The Otocyst as an Auditory Or- 



saii 



Methods 



1. Responses of Palaemonetes to 



Vibrations transmitted to 

 Water 



a. Xorinal Conditions . . . 



b. Poisoned with Strychnine 



c. Both Otocysts removed 



d. Removal of Antennaj and 

 both Antennules .... 



e. Meaning of these Experi- 

 ments 



2. Responses of Gelasimus pugi- 



lator 



a. To Vibrations transmitted 

 to Water 



b. To Atmospheric Sounds 



II. The Otoc^-st as an Organ of 



Equilibration 



1. The Removal of Sense Or- 

 gans and its Effect on Equil- 

 ibration 



a. Eyes blinded 



b. Both Otocysts removed 



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 223 



223 

 223 



223 

 223 

 224 



224 



224 



225 



226 



226 

 227 



228 



230 

 230 

 230 



c. Both Eyes blinded and 

 both Otocysts removed 



d. One Eye blinded and both 

 Otocysts removed . . . 



e. Both Eyes blinded and one 

 Otocyst removed .... 



2. Removal of Sense Organs 



and its Effect on the Com- 

 pensation Movements of the 

 Eyes 



a. Normal Animals .... 



b. Both Eyes blinded . . . 



c. Both Otocysts removed . 



d. Both Eyes blinded and 

 both Otocysts removed 



3. Equilibration of Animals nor- 



mally without Otocysts . . 



4. The Effect of the Develop- 



ment of the Otocj'st on the 

 Equilibration of Lobster 

 Larvae 



5. The Function of the Otoliths 



6. The Function of the Hairs of 



the Otocyst 



Summary 



Bibliography 



Explanation of Plates 



PAGE 



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232 

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23-t 



234 

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240 



242 

 246 

 251 



INTRODUCTION. 



Since the appearance of the admirable paper by Hensen ('63) on the 

 auditory organs of decapods, a period of thirty-seven years has ehxpsed, 

 a period rich in zoological discoveries and improvement in general tech- 

 nique. The great advances made in comparative neurology by means 

 of modern methods have reopened to investigators fields for research 

 hitherto considered exhausted. The zoologist of the present time ia 

 thus enabled to reap a second crop on ground already carefully gleaned, 

 and to harvest results as important as those originally obtained. 



The physiological work of Hensen's paper has been continued in re- 

 cent years by various investigators. But aside from the paper by 

 Bethe ('95) on the otocysts^ of the schizopod Mysis, little work has 

 been done on the morphology of the decapod ear since 1863, 



1 Throughout this paper the terms otocyst, statocyst, ear, and auditory sac 

 will be \ised synonymously to designate the auditory organ, 80-calIed, of Crustacea. 



