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Minute Inhabitants of Aquaria 



PERRY BRUCE CLARK 



San Francisco Aquarium 



Society? 



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The first step up on the plant side is 

 the group "Algae," the most simple 

 forms of it being single cells. It is this 

 form which is generally found in the 

 aquarium, being seen as a thin green 

 film on the sides (this film is composed 

 of countless numbers of these minute 

 cells). Another sometimes seen is com- 

 posed of fine, long, green threads. The 

 Algae obtain a part of their nourish- 

 ment, as do all other green plants, by a 





Four Species of Algae 



process known as photo-synthesis. 

 Through the action of light and the 

 chlorophyll or green coloring- matter 

 they are able to form synthetically 

 starch and cellulose from carbon diox- 

 ide and water. 



Another group of simple plants is the 

 Fungi. This group contains no chloro- 

 phyll, and is almost always parasitic. 

 They either live on another organism or 

 upon some organic matter. 



The next group is where the Algae 

 and the Fungi have combined and grow 

 together, being of equal benefit to each 

 other ; the Algae furnishing the nour- 



ishment and the Fungi protecting them 

 with their long threads. These plants 

 are called lichens. This is as far as we 

 will go with the plants, returning now 

 to the Bacteria and starting up on the 

 animal side, beginning with the Pro- 

 tozoa or single celled animals. 



The first cell which shows the funda- 

 mental characteristics of an animal, is 

 the Amoeba or proteus animalcule. This 

 small animal cell is usually found in the 

 slimy coating on submerged leaves and 

 stems in standing water. It is a small 

 speck of clear, colorless, jelly-like sub- 

 stance called protoplasm, with a distinct 

 though delicate outline. This cell con- 

 tains the nucleus, contractile vacuole 

 and food vacuoles. Amoebae move by 

 throwing out part of the cell into what 

 is called a pseudopod, which may be ex- 

 tended or contracted without changing 

 the place of the amoeba, but if it wishes 

 to move the whole body simply flows 

 into the extended pseudopod, another is 

 extended and the protoplasm flows into 

 the new one, etc. When an amoeba 

 comes in contact with a bit of food ma- 

 terial, such as a bacterium or fragment 

 of animal or vegetable cell, it flows 

 around the food, thereby ingesting it. 

 When the bit of food is ingested a small 

 amount of water is also taken in, and 

 this forms what is called a food vacuole. 

 Usually a number of these food vacuoles 

 may be seen in an amoeba in different 

 stages of digestion. If a grain of sand 

 or other indigestable matter is taken in, 

 it is soon passed out of the body, being 

 left behind as the amoeba moves along. 

 There is no mouth, food being taken in 



