578 THE POPULAR SCIENCE MONTHLY. 



their work is to destroy it. So, if the torula is not a mineral nor an 

 animal, it must be a vegetable. Vegetables are the manufacturers or 

 producers of protein ; animals are the destroyers or consumers of it. 1 

 You have now found that the torula or yeast-cell is a plant, and not 

 an animal. The next question is, What kind of a plant is it ? Mostly 

 all plants need the sun, but the yeast-plant grows as well in the dark 

 as in the light. Plants that need the light are always green ; they 

 take in carbonic acid, and give off oxygen, but the torula has no green 

 color, and it takes in oxygen and gives off carbonic acid. Those plants 

 which give off carbonic acid, grow in the dark, and are not green, are 

 called fungi. The mushrooms and toadstools are fungi. Now let us 

 see how many things you have learned about yeast : First, that it is 

 alive ; second, that it is a plant ; third, that it is a fungus. 



When first you try to study this lobster, you will perhaps think, 

 as I thought, " How can I straighten out such a queer, crusty, clawy 

 thing as that ? " But, though the lobster looks as hard as the Greek 

 alphabet, he is as easy as your own A, B, C, when once you find him 

 out. You know the corolla or crown of the bean looked so hard, but 

 it all came out nicely into five leaves, or petals, as soon as you knew 

 how. Now let us see if we can find and name the different parts of 

 the lobster. (You must have a real lobster before you to look at 

 while I talk. The crawfish or crayfish that lives in brooks and rivers 

 is fashioned after the lobster, only smaller ; so one of these can be 

 studied by those of you who live inland.) One tiling is very certain 

 he has a great many different parts, very unlike each other. First, 

 you see (Fig. 15), he is covered with a shell, which, like the mussel's 

 and clam's, is his exo-skeleton. This shell is very hard, like stone, 

 and it is colored purplish black with pale spots here and there. The 

 lobsters which you see in shops are always scarlet. When these poor 

 fellows are caught, they are plunged alive into boiling water, which 

 turns the black coat red. This outside shell or exo-skeleton is made 

 up of a great many different pieces, instead of two, as the mussel's ; 

 but those pieces are shaped and joined in such a way as to make three 

 divisions of the body a head, a thorax, or breastplate, and an abdo- 

 men. The head-piece of the shell is pointed in front, forming the 

 beak or frontal spine (Fig. 15). Behind this head-piece is a groove or 

 seam where the head joins the breast or thorax, making the two pieces 

 of shell which cover the head and breast all one. So the first and 

 second divisions of the body thus joined in one are called the cephalo- 



1 Such plants as the Venus fly-trap seem to be an exception to this demarcation be- 

 tween the two kingdoms. These plants really digest protein matter, being supplied with 

 what may be termed prehensile organs for capturing their prey. Dr. Hooker suggests 

 that these plants are not exceptional and singular ; that they simply continue through 

 life the process begun by the germ when it nourishes itself upon the ready-made food 

 stored up in the seed. 



