354 EDITH M. PRATT. 
Finally, particles of carmine were also seen in the stellate 
and spindle-shaped amceboid cells forming the so-called 
“ mesogleeal nerve plexus” (fig. 24). Some of these cells 
were kept under observation for a considerable time. They 
frequently remained in an active amceboid condition for quite 
an hour, then the pseudopodia would be withdrawn, and the 
cells would become rounded and inert. Such a condition is 
comparable with the rounded cells frequently observed in 
the mesogloea of stained preparations. 
These experiments substantiate the following facts: 
1. Solid particles of carmine are ingested by the endoderm 
cells of the mesenterial filaments, body wall, and endodermal 
canals (figs. 21, 22, and 24) ina manner precisely similar to 
the ingestion of food particles by the mesenterial filaments 
(fig. 9). 
2. The endoderm cells of the ventral mesenterial filaments, 
the body wall, the canals, and cords in the mesoglcea are 
frequently amceboid. 
3. The presence of ingested carmine particles in the cells 
of the mesogloeal plexus indicates that they have been con- 
veyed from the ccelenteric cavities of the zooids to portions 
of the colony apart, or even remote, from the zooid. 
4. The cells composing the so-called “ mesogloeal nerve 
plexus”? are amoeboid, and the so-called “nerve fibres” are 
really the pseudopodia of the ameeboid cells. 
5. The mesoglceal plexus is more intimately connected 
with the endodermal than with the peripheral ectodermal 
tissues, while the cells, apparently of the same nature as 
the endoderm, are frequently larger in the neighbourhood 
of the endoderm than near the ectoderm. 
These facts afford evidence that the so-called “ nerve cells 
and fibres” are really amceboid endoderm cells which 
wandered into the mesoglcea, forming with their pseudo- 
podial processes the more or less dense protoplastic mesh- 
work known as the “ mesoglcal nerve plexus.” 
Although it is well known that, in the embryonic stages of 
higher forms of life, ganglion cells have a certain power of 
