EXTRUSION OF THE WINTER EGG CAPSULE IN 

 PLANARIA SIMPLISSISSIMA/ 



FLOYD E. CHIDESTER, 



Fellow in Anatomy, The University of Chicago. 



About the middle of October, 1907, I chanced to note that 

 some of the Planaria siinplississiiua in one of my aquaria had 

 developed egg capsules. 



I immediately transferred a number of flatworms, including 

 those that had already formed capsules, and a few that had not 

 as yet developed them, to a small aquarium on my desk. While 

 examining one of the planarians and its capsule under the micro- 

 scope, I saw the movements connected with the extrusion of the 

 capsule. 



When first observed, the capsule lay lengthwise of the body 

 in the position indicated in Fig. i. 



Presently the capsule was turned by the movement of the body 

 of the worm until it occupied a position as indicated in Fig. 2, 



Fig. I. 



Fig. 2. 



Fig. 3. 



then slowly came to the position indicated by F'ig. 3, that is, at 

 right angles to the longitudinal axis of the body. 



This change in position necessarily increased the size of the 

 cavity in which the capsule lay, lacerating the tissue and permit- 

 ting easy egress. 



' Contributions from the Biological Laboratory, Clark University. 



226 



