OF INVERTEBRATE ANIMALS. 401 



Amongst the class of animalcules which are called Infusoria, on account of 

 their being found so abundantly in vegetable infusions of all kinds, we have 

 many of different shapes and sizes, habits and instincts. I have here a repre- 

 sentation of one of the smallest that is seen by ordinary microscopes, called 

 Monas termo, and which is not more than the Yoooii °f an mcft m diameter- 

 They are found to possess in their interior several little bags for the purpose of 

 receiving their food ; they are in fact stomachs, and on this account they have 

 received the name of Polygastrica. Monas termo is figured in the plate, Fig. 2. 



The propensities of these little creatures do not at all belie their structure ; 

 they are most destructive and voracious beings. Every drop of water they 

 inhabit is a constant scene of confusion and carnage, on account of their fero- 

 ciously preying on each other. This, however, is not their only food, for they 

 partake abundantly of the vegetable particles that float about in the water with 

 which they are surrounded. A singular point in the economy of these little 

 animals is their power of retaining their vitality ; although they die in their 

 natural element in the course of a few weeks, yet if allowed to become dry, they 

 will assume their activity on the addition of w r ater for years after. They are 

 found in all kinds of fluids, imparting life and activity to the pink dew-drop, 

 sparkling in the morning sun, and giving to every drop of the water of the ocean 

 millions of inhabitants.* They are found in almost every fluid taken up by 

 plants and animals as nutriment ; and in the fluid portions of plants and animals 

 themselves they exist in abundance, 



I have before observed that no-where in Nature do we find an exact ascending 

 scale of organisation, and accordingly, in the classification of the Animal King- 

 dom, we are frequently obliged, for convenience, to group its objects according to 

 their general properties. Now, then, if by taking the single property of being 

 invisible to the naked eye, I group together all animals possessing that property, 

 I should expect to bring together animals very dissimilarly formed, for the 

 Creator, in the exhibition of his power, does not display to us the most design in 

 the largest forms of created beings, but generally treasures up the most brilliant 



miserable; for the proportion of positive happiness must, we conceive, be in direct ratio to the 

 degree of development possessed by each animal. It follows, throughout the kingdom, that the 

 more organs appertain to the species, and the more complete these organs are, the more will the 

 creature enjoy itself, as long as it has the power of employing its organs in the manner intended 

 by Nature. The same law which holds good as regards physical matters, is strikingly illustrated 

 in mental nature. Thus Man excels all the lower animals in the number and quality of his 

 cerebral faculties, and has, therefore, a greater capability for happiness than the brutes. Those 

 men, moreover, who act rationally by the greatest number of faculties, and chiefly by the higher 



faculties, are, ceteris paribus, the happiest Ed. 



* Ehrenberg calculates that a single drop of water may contain 400,000,000 of some of these 

 Infusoria. 



