ties of the trache- 1 * <or bronchial tubes, through which air is imported by way of 

 the spiracles, and thus the blood is purified in a manner quite analogous to that in 

 which the blood of the higher vertebrates is purified and freed from waste matter 

 by oxydization. The process is, however, as has already been pointed out, mainly 

 carried on in the abdominal region, and not exclusively in the thorax, as in the case 

 of vertebrates. 



The nervous system of butterflies consists of a cord with ganglia, or nerve-knots, 

 one for each segment of the body. As there are thirteen segments in the body of a 

 butterfly, there are normally thirteen such ganglia, or nerve centres. The nervous 

 cord lies in a position exactly opposite to that which is held by the spinal cord in 

 vertebrates. It is situated on the ventral side of the body, and more ventrad than 

 all the other internal organs. The ganglion in the head is the largest of all and 

 forms a rudimentary brain, the greater portion of which consists of two relatively 

 large optic nerves. 



The internal organs of reproduction in the female consist of the ovaries, from 

 which the eggs pass by way of the oviduct to the ovipositor, which in butterflies is 

 not so conspicuous or remarkable an organ as is the case in many other insects. 

 Communicating with the oviduct are the spermatothecae, which are receptacles in 

 which is retained the fertilizing fluid received from the male at the time of coition. 

 As the eggs, one by one, are passed from the ovaries into the oviduct, they are im- 



