296 ALBERT KUNTZ 



At the close of the sixteenth day of incubation the anlagen of 

 the prevertebral plexuses have become more conspicuous, but, 

 like the anlagen of the sympathetic trunks, they are composed 

 of cell-aggregates which are more or less scattered (fig. 8, P.V.). 

 The limits of the anlagen of the several prevertebral plexuses 

 cannot be determined at this stage. The cell-aggregates com- 

 posing them are scattered to such an extent that traces of one 

 or the other of these plexuses are not wanting in any transverse 

 section in the entire region from the suprarenals to the posterior 

 limits of the hypogastric plexus. 



From the seventeenth to the twentieth day of incubation the 

 anlagen of the prevertebral plexuses assume more definite pro- 

 portions, but many lesser cell-groups still remain more or less 

 scattered. In the region of the origin of the iliac arteries, cells 

 wander mesially from the anlagen of the sympathetic trunks 

 and descend between the iliac arteries to give rise to a wedge 

 shaped cell-aggregate lying in the median plane of the body 

 just dorsal to the mesentery (fig. 9, S. C. G. ). In some sections 

 the ventral angle of this cell-aggregate projects slightly into the 

 mesentery, while a few cells apparently become separated from 

 it and wander ventrally toward the rectum. Continuous lines 

 of sympathetic cells could not be traced ventrally in the mesen- 

 tery, but in many sections in this region groups of nervous ele- 

 ments may be observed in the tissues associated with the walls 

 of the rectum (fig. 9, S. C. R.). This process of migration of cells 

 from the anlagen of the prevertebral plexuses in the posterior 

 region of the body toward the rectum, doubtless, begins at an 

 earlier stage. I was not able, however, to observe distinct 

 groups of nervous elements associated with the rectum until 

 about the nineteenth or the twentieth day of incubation. 



In the earlier paper referred to above the writer traced the 

 origin of the ganglion of Remak in the chick to cells which mi- 

 grate ventrally from the anlagen of the hypogastric plexus. 

 The ganglion of Remak in the chick is a conspicuous cell-column 

 more or less circular in transverse section lying in the mesentery 

 just dorsal to the rectum. Furthermore, the suggestion was 

 offered that the ganglion of Remak may have its prototype in 



