96 JOURNAL OF ENTOMOLOGY AND ZOOLOGY 



The first and second thoracic ganglia each have two pairs of 

 nerves. The last ganglion has a large lateral pair of nerves and 

 two terminal ones which run back a considerable distance to the 

 end of the body and give off branches. 



Other ganglia and nerves which may be parts of the so-called 

 sympathetic system are as follows : 



There is a small frontal ganglion, its posterior branches prob- 

 ably connect with the brain but the connections were not seen. 

 Back from this ganglion a small nerve follows the intestine and 

 at one place seems to give rise to lateral nerve centers on the 

 wall of the intestine. Running dorsally from the dorso-caudal 

 end of the subesophageal ganglion is a very small median nerve ; 

 it runs dorsally and then back to the first part of the first thoracic 

 ganglion. Between the next two ganglia there are similar 

 median nerves. A few slight fibers from these seem to go to 

 the intestines. Oudemans '87 in Machilis figures a similar 

 nerve and branches from it are spoken of as going to spiracles. 

 Neanura has no spiracles. 



In several species of Collembola studied in 1913 and 1914 I 

 have found no indication of such median nerves, but it is possible 

 that they were present and not seen in the smaller and less 

 favorable species. This median trunk in various conditions has 

 been figured in a number of species in recent times by Hammar 

 '08, and by Haller '10, but I have seen no mention of it in 

 Collembola. 



Some of the chief points in this study are as follows : 



1. The central nervous system is small in i^roportion as 



compared with other Collembola. 



2. A small frontal ganglion and two small intestinal ganglia 



were recognized. 



3. Median nerves run between all the ganglia but the first two. 



4. The brain seems made up of three ganglia fused, the 



subesophageal ganglion seems composed of several 

 fused parts and the last ganglion seems composed of 

 four or more distinct parts. 



