Ifo. 7. — Contributions from the Zoological Laboratory of the 

 Museum of Coinparative Zoology at Harvard College, under 

 the direction of E. L. Make, No. 123. 



THE OTOCYST OF DECAPOD CRUSTACEA: ITS STRUCTURE, 

 DEVELOPMENT, AND FUNCTIONS. By C. W. Pkentiss. 



TABLE OF CONTENTS. 



Introduction 



Parti. — Morphology .... 



A. Historical Survey . . . 



B. Observations 



1. Material 



2. Methods 



3. Structure and Development 



PAGE 



L Palfemonetes . . . 180 



1. Structure of the 



Otocyst . . 180 



n. Sac .... 180 



b. Sensory Cushion 181 



c. Structure of 



Hairs ... 182 



d. Formation of 



Hairs ... 182 

 «. Otoliths . . . . 184 



2. Innervation of the 



Otocyst . . 185 



a. Number of 



Nerve Ele- 

 ments to a 

 Single Bristle 186 



b. Periplieral Ter- 



minations . 188 



c. Central Termi- 



nations . .190 



d. Histology of 



the Nerve Ele- 

 ments ... 191 



3. Development of 



the Otoc3-st. 

 (In Homarus 



americanus.) 193 



a. 1st larval Stage 193 



b. 2d " " 194 



c. 3d " " 194 



d. 4th " - 195 

 e 



VOL. XXXVI. — XO. 7 



PAGE 



II. Crangon 196 



PAGE 



IV. Carcinus 20-4 



.... 205 



.... 205 



.... 206 



.... 208 



.... 211 



.... 211 



.... 211 



.... 212 



.... 213 



.... 213 



.... 213 



