420 MORPHOLOGY OF THE ABDOMEN IN THE ODONATA 



anterior segments of the abdomen. Beyond which they rapidly 

 narrow and finally in the seventh segment blend into the oviducts. 



The Oviducts are thus very short and quite wide, carrying 

 several eggs (two or three) side by side. They meet on the under 

 side of the bursa copulatrix. At the hind end of segment seven 

 they pass beneath the diapliragm covering the neural sinus. 



The Bursa Copulatrix varies in size depending upon its con- 

 tents. It is oval or round, and is covered anteriorly by the last 

 ganglion. Attached at its lower anterior part is a pair of finger- 

 like accessory sacs which extend caudad about its sides. A 

 ventral posterior extension of the bursa, a vagina, connects with 

 the genital .pore at the apex of the eighth segment. 



In a small cup-like depression in the sternum of the ninth seg- 

 ment lie two elongated glandular or sac-like bodies. Their con- 

 nections could not be made out clearly. 



These descriptions were made from specimens taken during the 

 period of active copulation in earlj^ April. 

 Nervous System 

 (Plate XXVI, figure 25, nc.) 



In the Anisoptera there is always a neural or sub-intestinal 

 sinus formed in the concavity of the sternum by its being covered 

 over by a sheet of membrane stretched between the tips of the 

 sternal processes and along the pleural fold at the sides of the 

 sternum. After the removal of the aUmentary canal this mem- 

 brane must be lifted away bit bj^ bit before the nerve chain is 

 bared. 



The Nerve Chain in Anax and Aeshna is very similar to that of 

 the Zygoptera. The ganglia are somewhat elongate and the 

 connectives are thin and close together. Each ganglion lies 

 about one third of the length of the segment from the anterior 

 suture. 



The Muscular System 

 (Plate XXVH, figures 31, 33, 34, 35, and 36) 



Both Anax and Aeshna have been carefully studied and com- 

 pared. Their organization seems identical except for sHght dif- 

 ferences in the strength of the muscles. The general description 

 of these species would also so nearly approach that of Calopteryx 

 that it seems best to note only the larger differences. 



