No. 3-] THE EMBRYOLOGY OF A TERMITE. 53I 



should be remembered, though, that the Termite's germ-band 

 exhibits no "macro-somites " of Graber, and that the disc lacks 

 the prominent gastrula groove of Stenobothrus. 



As a whole, the resemblance between the Orthopteran and 

 the Termite during the embryonic stages is striking. 



A stage corresponding to that figured by Brandt (3), Fig. 11, 

 for Calopteryx is reached, with the appearance of the mouth 

 and the labrum, and the subsequent folding of the head up 

 from the surface of the yolk. At the same time the segments 

 and appendages have become more prominent. 



The embryo, unlike the Libellulid, is not immersed in the 

 yolk. (See PI. XXXII, this paper, also Korschelt and Heider 

 (17), figures on pp. 774, 'j'j6, and 'jj']) 



In the Termite, when the germ-band has grown along the 

 dorsal surface of the yolk to the anterior end of the Q.%g, the 

 posterior portion of the abdominal region sinks slightly into 

 the yolk. As the embryo continues to elongate, this bend in 

 the abdominal region becomes more marked, the tail-end of the 

 band coiling ventrally into nearly a complete circle. (See dia- 

 grams, PI. XXXII.) 



This caudal flexure is a very characteristic phenomenon. It 

 occurs in many insects and is much like that of the Libellulid. 

 (See Korschelt and Heider (17), figures on pp. 774, 'j'j6, and 

 TTJ^ I cannot explain it. It certainly appears to take place 

 here (as in the Libellulid), without being necessitated by any 

 combination of mechanical forces that can be stated. 



The formation of this flexure has furnished me with a warn- 

 ing, and a good example of what at first sight appears to be a 

 simple mechanical process, but proves to be a phenomenon not 

 so readily dismissed. In many specimens, a very plausible 

 explanation of it seems to be the resistance offered to the 

 posterior end of the elongating germ-band by the chorion, 

 lying at right angles to its course at the anterior end of the 

 ^gg. This will not serve as an explanation, however, since in 

 many preparations the flexure occurs before the anterior end of 

 the egg is reached (as in the Libellulids). It is clear in one 

 instance, at least, that the tail end of the embryo might grow 

 back on the surface of the yolk around the anterior pole, as in 



