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matter is said to be luminous ; and it is to this 

 cause that the sparkling appearance of the sea 

 by night in some places has been attributed. 



In insects, the cuticle is always membranous ; 

 while it is the corpus mucosum which constitutes 

 their horny or calcareous sheaths, and forms, 

 also, in some, as spiders, flies, gnats, bees and 

 butterflies, the fine hairs, feathers or scales, with 

 which they are in certain parts invested. The 

 proper cutis again is below this, constituting, in 

 the lobster, for example, its membranous pellicle. 

 This part is, however, so completely defended, 

 for the most part, from the contact of external 

 substances, that to most insects are given in ad- 

 dition antennae, palpi, cirrhi, &c. called, in gene- 

 ral, feelers, situated commonly about the mouth, 

 and the chief seat, in them, of the function of 

 touch. 



The cuticle is membranous also in fishes, and 

 immediately invests their scales, as well as the 

 bristles of the stickleback, the tubercles of the 

 sturgeon, &c., all which are formed by the cor- 

 pus mucosum. Under this is the cutis ; but it 

 is often so well defended from external impres- 

 sions, that to many of these animals, as well as 

 to insects in general, nature has given cirrhi, or 

 other analogous organs, as an immediate instru- 

 ment of touch. 



In reptiles the cuticle is either membranous, 

 or, as in the frog, consists merely of mucilage, 

 as it does in many worms already noticed. The 

 corpus mucosum in these animals, assumes the 



T 



