TRANSFORMATIONS OF THE 



this stage of the animal's life are consummated ; 

 the fifth and sixth ganglia gradually disappear, so 

 that a long distance now intervenes between the 

 thoracic and abdominal ganglia, and those of the 

 latter region are no longer placed in the respect- 

 ive segments in which they first appeared. Many 

 of the nervous threads have in like manner become 

 amalgamated, and in all cases they have been 

 transported with the ganglia from which they orig- 

 inated, or they issue from the main nervous cord 

 at the points where the ganglia have vanished. 



But it is in the reproductive system that the 

 greatest transitions occur. The little sac and 

 thread on either side of the body, without outlet, 

 and only to be traced with difficulty in the cater- 

 pillar, have come to fill nearly the entire ab- 

 dominal cavity of the perfect insect. In one sex, 

 the little sacs first approach each other upon the 

 back and then increase in size and amalgamate in 

 one spherical body ; simultaneously with its in- 

 crease in size, the threads enlarge and lengthen, 

 and with their inextricable convolutions fill the 

 whole abdomen, and find their outlet next that of 

 the alimentary canal. In the other sex, the little 

 tubes of which the sac is composed separate ex- 

 cepting at the tip, increase wonderfully in size 

 and length, coil up and become distended with 

 eggs, finally weighting the body to such a degree 

 that the butterfly flies with difficulty ; while the 



