SILK-WORMS AND SERICULTURE. 



66 1 



comes back to the heart by veins. In making this circuit it finds on 

 its route the lungs filled with air by means of respiration. 



In our caterpillar we also find blood and a species of heart, but it 

 has neither arteries nor veins. The blood is diffused throughout the 

 body and bathes the organs in all directions. However, it ought to 

 respire. Here step in the openings of which I have spoken. They 

 lead to a system of ramified canals, of which the last divisions pene- 

 trate everywhere, and carry everywhere the air that fluid essential 

 to the existence of all living beings. In our bodies the air and blood 

 are brought together. In insects the air seeks the blood in all parts 

 of the body. 



I have sketched for you a caterpillar when it is full grown. But 

 you well know that living beings are not born in this state. The 

 general law is, small at birth, growth, and death. The caterpillar 

 passes through all these phases. 



Fig. 3. 



Fig. 4. 



Egg and First Age, lasting five days. (An 

 age is the interval between" two rnoultings.) 



Second Age, lasting six days. 



I pass around among you some samples of what we call seeds of 

 the silk-icorm. These so-called seeds are in reality eggs. The cater- 

 pillar comes out of the egg very small ; its length, at birth is about 

 one-twentieth of an inch. Look at these samples, and you will see how 



Fig. 5. 



Third Age, lasting 6ix days. 



Fig. 6. 



Fourth Age, lasting six days. 



Fig. 7. 



Fifth Age, lasting nine days. The mature worm near the end of its career, and at the time of 



its greatest voracity. 



great is the difference of size between the worm at birth and the full- 

 grown specimens I have shown you. This difference is much greater 

 than in man. A man weighs about forty times as much as the new- 



