8 SPHERE AND FUNDAMENTAL 



mal, which, although imperfect, is nevertheless a chicken ; 

 it has been developed from a hen's egg, and we know that, 

 should it continue to live, it would infallibly display all the 

 characteristics of the parent bird. Now, if there existed in 

 Nature an adult bird as imperfectly organized as the 

 chicken on the day, or the day before it was hatched, we 

 should assign to it an inferior rank. 



22. In studying the embryonic states of the mollusks or 

 worms, we observe in them points of resemblance to many 

 animals of a lower grade, and to which they at length be- 

 come entirely dissimilar. For example, the myriads of 

 minute aquatic animals embraced under the name of Infu- 

 soria, in their organization generally, very simple, remind 

 us of the embryonic forms of other animals. We shall have 

 occasion to show that the Infusoria are not to be considered 

 as a distinct class of animals, but that among them are 

 found members of all the lower classes of animals, mollusks, 

 crustaceans, polyps, and many of them are even found to 

 belong to the Vegetable Kingdom. 



23. Not less striking are the relations that exist between 

 animals and the regions they inhabit. Every animal has its 

 home. Animals of the cold regions are not the same as 

 those of temperate climates ; and these latter, in their turn, 

 differ from those of tropical regions. Certainly, no one will 

 maintain it to be the effect of accident that the monkeys, 

 the most perfect of all brute animals, are found only in hot 

 countries ; or that it is by chance that the white-bear and 

 reindeer inhabit only cold regions. 



24. Nor is it by chance that the largest of all animals, 

 of every class, the whales, the aquatic birds, the sea-turtles, 

 dwell in the water rather than on the land. And while the 

 water affords freedom of motion to the largest, so is it also 

 the home of the smallest of living things, affording to them 

 a freedom from obstacles to their motion, which they could 

 not enjoy elsewhere. 



