THE ANATOMY OF CHELYOSOMA PRODUCTUM 



STIMPSON. 



BY FRANK WATTS BANCROFT. 

 CONTENTS. 



PAGE. 



Plate XVIII. 



Introduction 309 



Range and External Appearance 310 



The Disk 311 



Union of the Plates 313 



The Test Matrix 314 



Cells In the Test 315 



Origin of the Yellow Layer 317 



Blood-vessels in the Test 318 



Union of the Muscles and Test 319 



The Musculature 320 



The Pharyngeal Apparatus 322 



The Branchial Sac 324 



The Viscera 326 



Conclusion 328 



Bibliography 330 



Explanation of Plate 332 



Introduction. 



Part of the material which formst he basis of this study 

 was derived from the collections of the University of Cali- 

 fornia, and the remainder from a very interesting lot of 

 Puget Sound ascidians which the Young Naturalist's Club 

 of Seattle sent to the University for examination. The 

 specimens were mostly alcoholic, but a few were fixed in 

 picrosulphuric or glacial acetic acid. 



The investigation was carried on under the direction of 

 Professor William E. Ritter, for whose constant kindness, 

 not only in connection with my research, but in many other 

 respects as well, I wish to express my most sincere 

 appreciation. 



The genus Chelyoso?na was established by Broderip and 

 Sowerby (1829) to accommodate the single species C. 

 maclcayanum, which, since then, has attracted considerable 

 attention and has been examined quite frequently, espe- 

 cially by Danish and Scandinavian authors. In conse- 

 quence of these investigations many anomalous characters 



[ 3°9 ] Sept. 16, 1898. 



