MINUTE ANIMAL LIFE. 
219 
as the mother did before it. You may say that the 
ameba can never grow old, for in the very vigor of 
life it becomes twins to start life over again. 
In our glass of water we may also find little bell¬ 
shaped vorticellidse attached by a stem. Many other 
microscopic creatures exist in this glass, but there is 
not room in this book to describe them. An enjoy¬ 
able description of such life is given in Mrs. Bayliss’s 
In Brook and Bayou. 
I can not leave this subject, however, without re¬ 
ferring to the Gregarina. These are minute organ¬ 
isms which live in the intestines of crayfish and of 
some insects. They attach themselves to the inner 
side of the alimentary canal, some by means of hooks, 
and live upon the liquid food in the intestines. 
In time they become a cyst by enveloping them¬ 
selves in a tough covering. The nucleus divides into 
numerous small elliptical bodies, which in various 
ways escape from the cyst as spores. These spores 
somewhat resemble the bacteria spores. Under suit¬ 
able conditions they develop into Gregarina. Al¬ 
though the Gregarina is far more complex than the 
ameba, it is still a single-celled animal, and belongs 
to the simplest class of animals. 
The water-beetle found in the same glass has legs, 
a head, and '^ther distinctive parts of the body. Each 
has its particular use. The nervous ganglia, which form 
its brain, control the muscles and other parts. The 
beetle, therefore, is composed of organs, and the or¬ 
gans are composed of different cells. It is, then, a 
very complex creature compared with the Gregarina, 
