142 BRUCE D. REYNOLDS. 



EXPLANATION OF PLATE I. 



FIG. i. Camera lucida sketches illustrating shattering reaction. A, Arcella 

 poly fora approaching a fragment from another individual of the same species, frag- 

 ment shown below. X i~o. B, The same bodies just after making contact. C, 

 A portion of B enlarged. 



FIG. 2. Diagram of vertical section illustrating shape of shell and position of 

 pseudopods. 



FIG. 4. An abnormal Arcella which appeared suddenly in a hay infusion culture 

 of clone Q, line qd. .4, Lateral view; B, Ventral aspect, showing ellipsoidal mouth; 

 C, normal individual of line from which the abnormal specimen was obtained. X 

 170 camera lucida. 



