168 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
PAGE 
C. Theoretical Considerations. . . 215 
1. Comparison of the Otocyst with the Vertchrae Ear 215 
2. Neuronsiheory, ©, = felis tsas sihensenem namely 
Part IT: —Physiologys,< 7 | < 2s," c. <euien eet Ones 
PAGE PAGE 
A. Historical Survey . . . 5 6 Pals! c. Both Eyes blinded and 
B. Experiments and Observations - 2238 both Otocysts removed . 230 
I. The Otocyst as an ere te Or- d. One Eye blinded and both 
Gai sweaters > . 223 Otoeysts removed . 231 
Methods assume 223 e. Both Eyes blinded ale one 
1. Responses of Palemoncees ts Otocyst removed . .. . 231 
Vibrations transmitted to 2. Removal of Sense Organs 
Water .. - « - 223 and its Effect on the Com- 
a. Normal Gandiionn So PPB! pensation Movements of the 
6. Poisoned with Strychnine 224 IDS Go 6 Newtons 
c. Both Otocysts removed . 224 a. Normal eee « 2 0 « 23e 
d. Removal of Antenne and 6. Both Eyes blinded . . . 2382 
both Antennules . . . . 224 c. Both Otocysts removed . 233 
e. Meaning of these aaa d. Both Eyes blinded and 
THEHES (aes 225 both Otocysts removed . 233 
2. Responses of Gata: see 3. Equilibration of Animals nor- 
FARO 5 6 226 mally without Otocysts . . 234 
a. To Wabentinnen fount 4. The Effect of the Develop- 
to Water .. . 226 ment of the Otocyst on the 
6. To Atmospheric Scents - 227 Equilibration of Lobster 
Il. The Otocyst as an Organ of Larve . 234 
Equilibration es 228 5. The Function of ‘the Otoliths 237 
1. The Removal of Sense On 6. The Function of the Hairs of 
gans and its Effect on Equil- the Otocyst’ “2 ee) sseemne et 
ibration . . “ 2 « « 230 | Summary «: =‘ (c) 20s) (onions 
@. Hyves blinded = = © < . 280) | Bibliography, . = <9. enieeneeeecan 
b. Both Otocysts removed . 230 | Explanation of Plates . PEM ey Pa 
INTRODUCTION. 
Srnce the appearance of the admirable paper by Hensen (’63) on the 
auditory organs of decapods, a period of thirty-seven years has elapsed, 
a period rich in zodlogical 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 zodlogist of the present time is 
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 used synonymously to designate the auditory organ, so-called, of Crustacea. 
