PROTOZOA. | 29 
appearance of a single cell, consisting of an ill-defined mem- 
branous envelope, filled with a more or less granular sarcode 
containing fatty granules, and having in it a little central 
bladder or vesicle—the ‘“nucleus”—which in turn encloses a 
solid particle or “nucleolus” (fig. 2, a). The outer covering or 
Fig. 2.—Anatomy and reproduction of the Gregarina of the earth-worm (after 
Lieberkiihn). @ Adult Gregarina; 4 The same ‘‘ encysted ;” ¢ With the contents 
broken up into pseudonavicelle; @ Free pseudonavicellze ; e¢ Contents of the 
pseudonavicellz when liberated. 
cuticle with which the protoplasmic body is enclosed, may be 
quite smooth, or it may be furnished with bristles or spines, 
and in some cases even cilia have been observed. Beyond the 
nucleus and nucleolus (which are probably connected with 
reproduction), no definite organs have been detected in the 
Gregarine ; and all the processes of assimilating food and 
getting rid of waste or injurious products must be effected 
by the general surface of the body. As we shall see, however, 
this is common in internal parasites, which are not necessitated 
to live upon solid food, but which are enabled to subsist. simply 
by imbibing the nutritive juices of their hosts. 
The following is a brief outline of the process of reproduction as it 
has been observed in the Gregaring, sometimes in a single individual, 
sometimes in two individuals which have come together and completely 
coalesced and melted into one another. The Gregarina becomes com- 
pletely motionless, assumes a globular form, and develops round itself 
a thick structureless coat or envelope, when it is said to be ‘‘ encysted ” 
(fig. 2, 6). The nucleus then disappears, and the sarcode of the 
body breaks up into little masses, which are at first rounded, but after- 
wards become pointed at both ends, when they are called ‘ pseudo- 
navicellz”’ (fig. 2, c), The cyst then breaks and the pseudonavicellze 
escape, when they give origin to little masses of sarcode, which have the 
power of active movement and of throwing out pseudopodia, thus com- 
ing closely to resemble the animalcule which will be directly described 
as the Ameéa (fig. 2, e). These little amceba-like masses, if they find 
a suitable locality, are finally developed into new Gregaring. 
