INTERNAL ANATOMY OF INSECTS. 25 



ably more than a third of its length a . On the fourteenth 

 day, the internodes, except the double ones, have be- 

 come nearly straight again; the fourth and fifth gan- 

 glions have coalesced so as to form one, and the sixth 

 and seventh have each lost their pairs of nerves 5 . Shortly 

 after this, these last ganglions have nearly disappeared, 

 and the chords of the three first internodes have again 

 approached each other c . The next change exhibited 

 is the absorption of the first ganglion by the brain, the 

 union of the chords of the first internode, which is now 

 straight, the approximation of the second and third gan- 

 glions, and the enlargement of the one formed by the 

 union of the fourth and fifth, at the expense perhaps of 

 the sixth and seventh, which have now intirely disap- 

 peared, and in their place is a very long internode. 

 These united ganglions retain the pairs of nerves they 

 had when separate 11 . Just before the assumption of the 

 imago, the direction of the lobes of the brain becomes 

 horizontal, the second and third ganglions unite, and the 

 internode between the third and fourth is shortened e . 

 Lastly, when the animal is become a butterfly, the se- 

 cond and third ganglions have coalesced, and are joined 

 to that formed by the union of the fourth and fifth ; a 

 short isthmus or rather constriction, with an orifice, 

 being their only separation : each of these united gan- 

 glions send forth laterally four pairs of nerves f . In his 

 figure, Dr. Herold has not represented the orifice for 

 the passage of the gullet, but doubtless one exists, which 

 for an animal that imbibes only fluid food is probably 



a PLATE XXX. FIG. 3. b Herold Schmeit. t. \\.f. 6. 



c Ibid. t. ii./. 7. d PLATE XXX, FIG. 4. 



c Ibid. FIG. 5. c Ibid. FIG. 6. 



