468 INSECTA. 



the gut, lie duets of a yellow colour, like thread, making two or three 

 folds on one another, and at the beginning of the intestine they open 

 into it. There is nothing answering to a liver or pancreas, excepting 

 these thread-like ducts are such. Silk- worms eat an immense quantity ; 

 but their power of digestion is very weak, for the food passes out of the 

 body very little changed, only a little darker in colour, and almost dry. 

 When their excrements are steeped in water they unfold themselves 

 like tea-leaves, and appear green and fresh again, and consist of the 

 small pieces of leaves the caterpillar had bitten off, to appearance not 

 the least altered. 



Immediately on the outer surface of these digestive organs are the 

 silk- vessels and ducts 1 ; they are placed laterally, and consist of two 

 canals, one on each side : they begin by a small blind end near to the 

 posterior part or tail of the animal, then pass forward, and are pretty 

 much convoluted : in their passage they approach more and more on the 

 lower part of the belly, where they become straighter, being only folded 

 on themselves in pretty long folds ; and in this course they expand, and 

 at last are pretty large : at this part appears to be the gland. Prom 

 the thick termination arises a very small duct, or, it may be said, that 

 the thick part contracts quickly into a small duct, which passes along 

 the under surface of the stomach to the head, where the communication 

 takes place with the one on the opposite side. 



Of the Silk Mucus. — This mucus is of a yellow colour in the thick 

 part of the duct, while it is clearer in the smaller part. It is thick and 

 ropy, more so than the white of an uncoagulated egg. It seems to 

 consist of two parts, one similar to the coagulable lymph, which coagu- 

 lates upon exposure, and even in water, and will not mix therewith ; 

 but, while endeavouring to mix this mucus with water, another part is 

 separated which readily mixes with the water, and tinges it, which is 

 the only way by which we know it has mixed with the water, leaving 

 the coagulable part white. Tbis part, by standing in the water, forms 

 the whole into a yellow jelly; which, when dried, cracks into separate 

 portions, and is capable of being softened again, but does not resume its 

 jelly-form again, like dried glue or gum. 



From the dark spots on the skin, or openings of the air- duets, we 

 find a number of dark canals leading inwards, which, as they pass, 

 ramify on the whole internal parts like arteries. All these openings 

 communicate with one another by a dark canal, passing from one to 

 another immediately on the inner surface of the skin. 



The general cavity of the body is enclosed in a muscular covering, to 



1 [Hunt. Preps. Phys. Series, Nos. 2985—2989.] , 



