HUXLEY, ON CLASSIFICATION. (gt 
most conspicuous of those phenomena, which we ordinarily regard as 
signs of life, which they exhibit, is a certain contraction aud expan- 
sion along different diameters, the body slowly narrowing, and then 
lengthening, in various directions. Under certain circumstances 
(though the conditions of the change are not thoroughly understood), 
it is observed that one of these Gregarinida, whatever its form may 
be, will convert itself into a well-rounded sac, the outer membrane 
ceasing to exhibit any longer those movements of which I spoke, 
Fig. 1. A, Gregarina of the earthworm (after Lieberkuhn); B, encysted; 
C, D, with the contents divided into pseudo-navicelle; E, F, free pseudo- 
navicelle; G, H, free amcebiform contents of the latter. 
and becoming coated by a structureless investment, or “cyst” 
(Fig. 1, B). 
The substance of the body contained within the cyst next under- 
goes a singular change. The central nucleus and the vesicle disap- 
pear; after a time, the mass breaks up into a series of rounded 
portions and, then, each of these rounded portions elongates, and, 
“VOL. IV.—NEW SER. aga 
