.30 EVOLUTION OF LIFE. 
simple and characteristic structure, and turn to the other 
descendants of Amcebe, as seen in Tree I. 
GREGARINZE. 
In the alimentary canal of the earth-worm, of cockroaches, 
etc., are often found sac-like bodies, called Gregarinze. (Fig. 
10.) These simple creatures are nearly destitute of organs, 
having simply in one part of their body a small nucleus and 
nucleolus, and a delicate muscular fibre. Nourishing itself 
by imbibing the juices of the animal in which it lives, 
slowly narrowing or lengthening its body in different direc- 
tions,- -this motion being probably caused by the delicate 
muscular fibre just mentioned,—the Gregarina passes its 
existence. At times, however, this motion ceasing, it takes 
the shape of a sac. (Fig.10, 4.) The nucleus and nucleolus 
disappear. The substance of the body breaks up into 
what have been called pseudo-navicelle, from their resem- 
blance to the Navicula. The contents of the navicelle 
(Fig. 10, d) are changed under favorable circumstances into 
Ameeba-like bodies (Fig. 10, e, f, g, A), which, in their 
turn, become Gregarine. By looking at Tree I. we see 
Amebe, or their haired descendants most likely, divided 
into four groups:— Ist, the Sponges, whose supposed 
progeny we have treated of as Coelenterata; 2d, Gregarinz, 
whose Ameeba-like development clearly indicates their 
ancestry, which we now leave ; 3d, Infusoria, whose young 
show in a marked degree their affinity to the Amcebz and 
to the Worms; 4th, the Noctilucz, the animals (allied to the 
Infusoria) causing the phosphorescence of the sea by the im- 
mense numbers of them found together in tropical climates. 
INFUSORIA. 
The animalcula of ditches and ponds are made up, in a 
great measure, of the microscopical beings called Infusoria. 
