No. 634] ORAL MEMBRANES OF GLAUCOMA 431 



long as broad, with one extremity enlarged and rounded, 

 and the other slightly narrowed and with a crescentric 

 edge (Fig. 4). They are joined at their base, at either 

 end, and project outward from the body so as to be 

 plainly visible in profile (Fig. 2). Usually the lips are 

 in constant motion, but occasionally may be seen inac- 

 tive, and when so are normally closed (Fig. 1). 



When the body of Glaucoma is disintegrated with 

 strong alum solution, or copper sulphate, it is sometimes 

 possible to isolate the two lips together, they apparently 

 being more resistant than the rest of the body. When 

 this is done, it can be seen that they are more nearly oval 

 in outline, possessing an extended, fin-like portion, which 

 projects into, or beneath the cuticle (Figs. 4 and 5). 



That the origin of these membranes may be sought for 

 in the fusion of rows of cilia situated on either side of 

 the buccal cavity, is suggested by the fact that each lip 

 exhibits striations running at right angles, or nearly so, 

 to the longitudinal axis (Fig. 6). These striations are 

 broadest at their bases, and narrowest at their tips, and 

 recall to mind the rows of stout oral cilia found among 

 so many of the infusoria. 



Between the bases of the lips lies the opening of the 

 buccal cavity, or mouth proper. Its edges, which may 

 be termed the inner lips, are also capable of a motion 

 which will be described later (Fig. 7). 



The movement of the outer lips consists of a rapid 

 opening and closing, and is best described by the word, 

 beating. The rate of the beating is apparently under 

 control of the animal, and varies at different times. 

 Under normal conditions the beating of the lips is very 

 rapid. The hyaline membranes, even when at rest, seem 

 to glisten, possibly due to the striations which refract 

 the light in different ways, and when in rapid motion 

 produce the pretty scintillating effect which has given 

 the creature its name. Observations made by the writer 

 of the rate of opening and closing of the lips, showed 

 that it varies from eight or nine times per second, through 



