432 University of California l'ii/i/irations in Zoology [VOL. l 



well flattened out by surface tension for about an hour, the flatness 

 persists for a time after a drop of water has been added, but gradually 

 the body recovers its normal form, usually within half an hour or less. 

 During an incision, short furrows frequently appear on either side of 

 the needle (fig.l). These may remain for some time but eventually 

 disappear. 



Any apparent modification in the shape of Euplotes patella occurs 

 only from extraneous pressure.' That the animal of itself is unable to 

 vary its shape may be observed when it is hemmed in by cotton or silk 

 fibers partially sealed to the cover-slip. Paramecia in the same hang- 

 ing drop force their way among the fibers through narrow passes with 

 constrictions of the body, a feat quite impossible to E. patella. Further 

 contrast in the pellicles of these two forms is seen upon adding a weak 

 solution (.1 per cent) of tannic or acetic acid. "Blisters" quickly 

 appear on Paramecium but not on E. patella, although both may die in 

 the solution within a few minutes. 



FIBRILLAR SYSTEM 



Studies of the fibers and their relations were made by means of 

 various dissections but the most satisfactory observations were had 

 when a slow disintegration of the body was brought about by inducing 

 delicate changes of surface tension with a V-shaped needle. There- 

 upon the fibrillar system and its attached organelles would often 

 remain intact and were always the last part of the body to undergo 

 disintegration. 



The anal cirri fibers normally lie upon the inner surface of the 

 ectoplasm just above ventral grooves which are formed by clcarly 

 defined ridges. Each ridge is chiefly composed of a single row of very 

 large ectoplasmic granules (fig. 20) that at times present internally a 

 finely granular appearance and often persist several minutes after 

 the body has entirely disintegrated. Sometimes they have been seen 

 to swell and burst explosively, disappearing entirely from view. These 

 and surrounding smaller ectoplasmic granules lie embedded in a 

 hyaline, gel matrix which apparently is continuous with the basal 

 plates of the anal cirri. This region of ectoplasm resists disruption 

 longer than the adjacent portions and so it frequently happens that 

 the anal cirri fibers, which lie upon the inner surface of the ectoplasm, 

 all remain intact after the complete disintegration of the body. This 

 condition, however, does not long prevail. Soon the ectoplasm here 



