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CHAPTER I _ 
Introductory 
HE large collection of living animals belonging to 
the Zoological Society contains at any given 
time representatives of all the principal families of 
vertebrated animals, as well as a few invertebrates, 
such as insects, scorpions, and the like, which latter are 
harboured in the Insect House. The great wealth of 
that collection will give some notion of the extreme 
productiveness of Nature, and will also emphasize the 
great uniformity which underlies so much superficial 
diversity. With its wild, that is uncaged, inhabitants 
the Zoological Gardens represents in a few square yards 
the animal. population of the globe. For all the great 
groups into which animated nature can be divided have 
here their representatives. Animals, in fact, fall into 
only about a dozen main groups or Phyla. At the 
bottom of the series we have the unicellular organisms, 
as a rule of minutely microscopic size and rarely visible 
at all to the naked eye; these comprise an infinite 
variety of creatures, called by the earlier investigators 
Infusoria, since they appeared in infusions of organized 
matter. There is not a pool or even puddle in the 
Zoological Gardens which has not its population of 
Amoebe and many other of these Protozoa. The 
remaining Phyla are multicellular organisms collectively 
termed Metazoa. The first group of the Metazoa, that 
of the Sponges, may perhaps be represented by the fresh- 
Z.G. I B 
