464 WILSON. 



EXPLANATION OF PLATES. 



All of the figures, unless otherwise stated, were drawn with the aid of the camera, 

 but in many cases the finer details have been added free-hand to the camera sketch. 

 Most of the figures were drawn from a single specimen, but in a few cases, in order 

 to economize space, a single figure combines the sketches from more than one speci- 

 men. In the later stages, for the most part, no attempt has been made to reproduce 

 the texture of the protoplasm, but it is of such glass-like transparency that it is fairly 

 well represented by the shading of the figures. The coloring of the figures was an 

 afterthought, and was adopted for purely practical reasons. Although the effect of 

 the drawings is injured by it, so much is gained in clearness and facility of compari- 

 son that I feel sure of the approval of every reader who has labored through with a 

 long series of imperfectly described plates. 



All of the figures, unless otherwise stated, are from N. limbaia, Ehlers. The 

 enlargement is in most cases about 400 diameters. 



