36 BULLETIN OF THE 
spaces, but more frequently at this stage contain a spherical body, which 
frequently fills the entire vacuole and is more refractive than the sur- 
rounding plasma (Fig. 59). Not unfrequently one sees a less refractive, 
clear space, surrounding the highly refractive body (Iig. 57). 
The description just given corresponds to the condition seen in a ter- 
minal branch whose polypide has attained the development of that shown 
in Figure 28 (Plate 111.). At the time immediately preceding the ori- 
gin of the bud, the cuboidal cells of the mesoderm show traces of vac- 
uolation, but their form and size have suffered no appreciable disturbance. 
This vacuolation of cells proceeds hand in hand with the development of 
the bud, and one first notices the homogeneous, highly refractive bodies 
in the vacuoles when the bud is well established. At about the time the 
alimentary tract has become formed, the reticulated cells begin to show 
sigus of degeneration. The highly refractive bodies have disappeared, 
and the skeleton of the cell which remains becomes very irregular. As 
already stated, the number of reticulated cells also decreases, until, at 
about the time of “rotation” of the polypide, there are few reticulated 
cells in the mesoderm, but these few are filled with vacuoles and their 
highly refractive bodies. 
The conditions of the mesodermal cells at the tip are slightly different 
from those found elsewhere. Usually, instead of many small vacuoles, 
one finds only one or two which fill almost the entire cell, — sometimes 
perfectly homogeneous in structure, sometimes containing small highly 
refractive granules. 
These appearances I believe to be explicable only upon the assumption 
that the mesodermal cells are capable, at the time at which the young poly- 
pide is arising, of imbibing the fluids of the body cavity and storing them 
up for the purpose of supplying the rapidly growing cells of the bud with 
nutrition. It is desirable to show reasons for believing, first, that the 
contents of these cells are nutritive matter ; secondly, that this has been 
taken up from the body cavity; and, thirdly, that it is supplied to the 
bud for its nutrition. 
It must be admitted that the strongest argument for the belief that 
these are absorbing cells is derived from a comparison of the appearances 
which we find in these cells with those described for Protozoa, and by 
Metschnikoff (83, Taf. I. Figs, 18-35) for mesodermal trophic cells. 
At the same time, it must be acknowledged that similar cells are found 
in other cases where the function is believed to be not ingestive, but 
excretory, as in the chlorogogen cells of Annelids, as shown by Kiiken- 
thal (85), Eisig (87, pp. 751-762), and others, and indeed even in the 
