132 THE DISTINCTION BETWEENj 



animal, and organized life as manifested in another form, the 

 plant, 



In beginning a description of the Animal Kingdom, the first 

 question that arises is, ''What is an animal?" By what char- 

 acters do we distinguish the animal from the plant? To the 

 generality of people it would seem as if the question would be 

 answered as soon as asked. No one, say they, would confound 

 a man with a tree ; a fish with a sea-weed ; a coral with a mush- 

 room, or a sponge ; but to show at once how soon the very dif- 

 ficulty would be plunged into, by instituting such a running 

 comparison, I will tell you that Ihe sponge has been, for years, 

 the centre of controversy as to its animal or vegetable nature. 

 The common, every-day acquaintance with the sponge would 

 not help one to distinguish it from certain kinds of corals which 

 I could produce. There are also other species of sponges which 

 are filled with limestone ; and they cannot be distinguished from 

 certain corals except by the closest scrutiny of the naturalist, and 

 sometimes in the fossil state the separation is impossible. This 

 is only one out of many instances of the kind ; and that you 

 may fully appreciate the hesitation of naturalists, of all faiths, 

 in determining the limits between the animal and vegetable 

 kingdoms, I will illustrate certain phenomena which occur 

 where the uninitiated would least suspect. 



From the early days of the microscope, when it was looked 

 upon rather as a marvellous sort of plaything, up to the time, 

 about 1826, when Ehrenberg began his researches upon the 

 more minute organisms, all those infinitesimally small moving 

 bodies which were seen by the earliest observers in various kinds 

 of fluids, whether water from the ocean, or streams, ponds, 

 stagnant pools, ditches, or decomposing fluids, such as old milk, 

 or in sour paste, or starch, &c., were believed to be Infusorial 

 animals. 



Notwithstanding that Vaucher, as early as 1803, had seen 

 that certain of these minute moving bodies burst forth from the 

 interior of one of the common fresh-water plants (Confervae), and 

 developed into fixed stems and branches, like those of the plant 



