PROBLEM I 



The Kinds of An'nnals of the Earth 6 1 



holes. Sponges grow fastened to the floor 

 of tropical seas from which they are torn 

 by dredges or cut loose by divers. After 

 they have been killed they are hung in 

 the air until the animals have decayed. 

 Then the sponge is washed in water until 

 nothing but the skeleton of the colony is 

 left. 



PHYLUM - PROTOZOA 



The First An'nnals 



What are the protozoa? The nn\ 



masses of living matter making up the 

 bodies of all animals and plants are called 

 cells. The common animals and plants 

 you know are made of billions and bil- 

 lions of cells. But some animals and plants 

 are made of only a single cell. As you 

 would expect, such animals and plants 

 are tiny, usually so small that they can 

 be seen only by means of a microscope. 

 The group of one-celled animals is called 

 the Protozoa, which means "first" or sim- 

 plest animals. 



Protozoa are found living in many dif- 

 ferent places. Ponds and streams are often 

 crowded with them, although the water 

 looks clear. Some parts of the ocean are 

 thronged with protozoa, as you will read. 

 There are protozoa that live in the intes- 

 tines of animals, and others that may live 

 in our blood and cause serious illness 

 (malaria). Altogether, they are as fasci- 

 nating a group of animals as we know\ 



Raising protozoa. It is easy to raise 

 protozoa in hay infusions. You can make 

 one by putting dried grass or hay into 

 water which is then permitted to stand. 

 Make a hay infusion accordingr to direc- 

 tions in Exercise io. As the hay decays, 

 some of its food materials dissolve in the 



Fig. 87 This jellyfisb has a long tube tbrorigb 

 which it eats. With its tentacles it catches and 

 paralyzes its prey, (aivierican museum of nat- 

 ural history) 



PHYLUM - PORIFERA 



Anijnals Riddled with Holes — Sponges 



The sponge. Only a few kinds of Por- 

 ifera (pore-if'er-a) produce commercial 

 sponges. The commercial sponge is the 

 tough, fibrous covering or skeleton of 

 many sponge animals that live in colonies. 

 The body of a sponge animal, like the 

 body of the sea anemone and coral ani- 

 mal, is a simple sac but this sac has many 



