92 THE PHILOSOPHY 



fccond time to the heart, immediately unite, and form nn 

 aorta defcendens, which fends off branches to fupply all the 

 parts of the body, except the gills. From the extremities 

 of thefe branches the blood is coUedted by veins, and return- 

 ed to the heart neariyin the fame manner as in other animals. 



The organs by which the nutritious part of the food of 

 fiOaes are extracted and conveyed to the general mals of 

 blood, and known by the names of lacSleal, abforbent, and 

 lymphatic velTels, are fo analogous to thofe of men and quad- 

 rupeds, that it is unnecelTary to defcribe them. For the 

 fame reafon, no defcription (hall be given of the nerves, 

 which, as in other animals, proceed from the brain and fpinal 

 marrow, and are diflributed over every part of the body. 



Having finiflied this fketch of the ltru6lure and organs of 

 iiflies, it is almoft needlefs to remark, that, though they live 

 in a different element, and vary greatly from land animals in 

 figure. Nature, in the formation of their bodies, in the mode 

 of their nutrition, refpiration, and fenfation, has acted upon 

 the fame great and general plan. 



We are now to take a view of the flrudure of infe<Sls, a 

 numerous clafs of animals, moft of whom recede farther 

 from the common mode of animal organization than any of 

 the other claffes. 



OF THE STRUCTURE OF INSECTS. 



In the firft chapter, a few obfervations were made con- 

 cerning the ftruclure and organs of infecSls, in order to fhow 

 more clearly the analogies betv/een animals and vegetables. 

 Thefe it is unneceffary to repeat. We fhall therefore pro- 

 ceed to a more particular examination of the flru^lure of in- 

 fers, and to trace the connetlHiion between that and their 

 manners. 



Infects exhibit fuch an immenfe variety in figure, colour, 

 and difpofition of parts, that Naturalifts have found it necef- 



