278 WILLIAM A. KEPNEF. 



EXPLANATION OF PLATE I. 



FIG. i. Nematocyst with its associated cell. Obtained by gentle pressure of 

 cover-glass upon a specimen treated with a drop of i per cent, acetic acid. Free 

 hand drawing, with aid of micrometer eye-piece. Xi,8oo. 



FIG. 2. Same cell after lying ten minutes in the dilute acetic acid. Vesicle 

 has formed at one end of cell. Free-hand drawing, with aid of micrometer eye- 

 piece. Xi,8oo. 



FIG. 3. Anterior end of Ch&togaster. Free-hand drawing. 



FIG. 4. Setae taken from lumen of enteron of sectioned Microstoma. Camera 

 lucida drawing. Xsoo. 



FIG. 5. Endodermal cell. Nematocyst lying within vacuole, V, at base of 

 cell; M, basement membrane of endoderm. Camera lucida drawing. XI.SOQ. 



FIG. 6. Nematocyst within vacuole, V, lying near middle region of mesoderm; 

 A, supporting cell of mesoderm; B, wandering cells of mesoderm; E, ectoderm; M, 

 basement membrane of endoderm ; P, pseudopodium (?) of wandering cell. Camera 

 lucida drawing. X 1,500. 



