344 



SECOND CHAPTER. 



OF NUTRITION. 



214. 



HAVING now, in the preceding chapter, pursued the history of the 

 formation and development of the insect embryo, proceeding from the 

 most general phenomena of generation, and then directly applying 

 them to the class of insects, I shall therefore now closely investigate 

 the progressive advancement of the young, now rendered independent 

 and excluded from the egg, and investigate the means whereby its 

 development is attained. For this purpose we take the insect in its 

 present stage, as it now exhibits itself, either as maggot, caterpillar, 

 or larva, without asking why it assumes this or that peculiar form, 

 reserving the answer to that question to the following chapter of 

 " Somatic Physiology," where it will receive its reply, in connexion 

 with the inquiry into the forms of perfect insects in general ; and we 

 therefore now direct our attention to the means appointed for the fuller 

 development of the individual itself. 



These are found to consist in its nutriment, namely, in the assi- 

 milation of the newly received organic substances. The young larva 

 must feed upon fresh organic matter, either vegetable or animal, and 

 transform it into its own substance if it is to live. An inquiry into 

 the several kinds of food, and their modes of reception and assimi- 

 lation, will constitute the subject of the ensuing chapter. 



215. 



If we take a general survey of the process of nutrition in general, 

 as we find it in the progressive development of animal organisation, we 

 shall perceive that an internal cavity presents itself as its first 

 organ. In this cavity, which is called the stomach, the food is 

 received, transformed, and the unassimilating portions rejected either 

 through the same orifice at which it was received (the mouth), or at 

 another aperture placed at the opposite extremity of the cavity of the 

 stomach (the anus). So long as the food remains in this sometimes 

 simple or tubular cavity, which is occasionally furnished with auxiliary 



