182 EVENINGS AT THE MICEOSCOPE. 



gular point formed by the two slender tubes at their 

 junction in the reservoir ; thus compressing the thread 

 of gum, and so preventing any more from issuing. The 

 gum is perfectly colourless in the reservoir, but as it 

 issues forth becomes coated with a varnish, which is 

 secreted in the same organ, and which is poured out at 

 the same time. In the case of the common Silkworm, 

 this varnish imparts to the silk that brilliant yellow hue 

 which it generally possesses, and which, as the varnish 

 is soluble, can be easily discharged from it in the man- 

 ufacture. 



