NERVE SYSTEM. 5 I 



in each case fuse into one, reducing the ganglia to 

 thirteen, as we have them in A, Fig. 11, where, of 

 course, the two first ganglia, lying over one another 

 nearly, appear in actual contact. But when the old 

 digestive tube lining and contents have been cast 

 away (see page 22), and the chrysalis stage is reached, 

 metamorphoses proceed more rapidly. The two latter 

 thoracic and two first abdominal ganglia then unite, 

 forming a large and powerful nerve mass (as seen 

 at B, Fig. 11), still giving indications of its com- 

 pound origin, and initiating the main external 

 activities of the insect by throwing out, from its 

 anterior parts, nerves to the second pair of legs 

 and the anterior wings, while its posterior half gives, 

 similarly, energy to the third pair of legs and the 

 posterior wings, the front legs receiving twigs from 

 the first thoracic ganglion. The original eight 

 abdominal ganglia, but now reduced to six (see 

 supra), suffer a further diminution in number by 

 the fourth and fifth melting together ; and so we 

 find, in the worker, five abdominal ganglia, while, for 

 reasons given when treating of the queen and drone, 

 they have four each only. But let us not imagine 

 that coalescence and development are all that occur. 

 The larva had needs which it does not carry with 

 it when it leaves the cell, and so some structures 

 are atrophied, with the nerves supplied to them, 

 while their material, by absorption, is diverted to 

 other uses. These changes require much patient 

 investigation in order fully to trace them, but they 

 may in large part be easily seen by proceeding with 

 eggs and larvae of various ages, as stated on page 37. 



F 2 



