•226 
IOWA ACADEMY OP SCIENCE 
2. The prevertebral plexuses arise from cells which migrate ventrally 
from the primary sympathetic trunks. 
3. The ganglion of Remak arises as an oval cell-column lying in the 
mesentery just dorsal to the rectum. It is composed of cells which mi- 
grate ventrally from the hypogastric plexus. 
4. Cells migrate from the neural tube and the spinal ganglia along 
the spinal nerves. Some of these cells deviate from the course of the 
spinal nerves and give rise to the sympathetic trunks. 
5. The vagal sympathetic plexuses : auz., the cardiac plexus and the 
sympathetic plexuses in the walls of the Ausceral organs arise from cells 
which migrate from the hand-brain and the vagus ganglia along the 
fibers of the Auxgi. The myenteric and the submucous plexuses in the 
posterior region of the intestine proliably receive some cells from the 
ganglion of Remak. 
6. The cells which migrate from the neural tube and the cerebro- 
spinal ganglia are the ‘Indifferent” cells and the “neuroblasts” of 
Schaper. Therefore, they are homologous with the cells giving rise to 
the neurones and the neuroglia cells in the central nerAmus system, and 
the sympathetic neurones are homologous with the efferent and afferent 
components of the other functional dhusions of the peripheral nerAmus 
system. 
7. Morphogenetic differences obviously indicate that the sympathetic 
system has departed more Avidely from the original type in birds than 
in mammals. 
