Vol. XXXII. June, 1917. No. \. 



BIOLOGICAL BULLETIN 



A STUDY OF DESICCATION IN THE ROTIFER, 

 PHILODINA ROSEOLA, WITH SPECIAL REF- 

 ERENCE TO CYTOLOGICAL CHANGES 

 ACCOMPANYING DESICCATION. 



LOUIS MAX HICKERNELL. 



CONTENTS. 

 I. Introduction . . 344 



II. Material and Methods ... 347 



III. Observations --.350 



1. On Entire Animals . 350 



A. Anatomy of P. roseola ... 350 



B. The Active, Free-swimming Animal. . . . 353 



C. The Contracted Animal .... 355 



D. The Dried Animal . 356 



E. Animal Recovering from Desiccation 357 



2. Sections 357 



A. The Normal Extended Animal 358 



a. Head Region 358 



b. Esophagus and Salivary Glands ... 359 



c. Mid-body Region 360 



d. Mid-body Region Containing Egg 360 



e. "Blasendarm" 361 



/. Foot 362 



B. The Contracted Animal 363 



a. Arrangement of Organs in Folded Condition 363 



C. The Dried Animal 363 



a. General Arrangement of Organs 363 



b. Detailed Comparison of Tissues of each Organ with Cor- 



responding Ones in Dried Specimen 364 



c. The Time at which the Rearrangement of Cell Elements 



Takes Place 368 



D. Animals Recovering from Desiccation 371 



a. General Arrangement and Structure of Organs 372 



b. Detailed Comparison of Tissues of Each Organ with 



Corresponding Ones in Dried and Undried Specimens. 374 



IV. Discussion 376 



V. Summary 393 



VI. Literature Cited .... 395 



VII. Explanation of Figures. . . . 398 



343 



