6 BULLETIN OF THE 
the surface after staining in hematoxylin, it appears uniformly dark. 
The mesoderm of the tip is highly modified, and a description of it 
will be more instructive after I shall have described the normal coelomic 
epithelium, as I shall do later. 
Passing from the extreme tip towards 8 (Fig. 14), one finds the ecto- 
dermal cells gradually changing in form, size, and structure, and becoming 
slightly broader, and very much shorter. Their nuclei lie near the inner 
ends of the cells, possess a thick “ nuclear membrane,” and are more 
nearly spherical than those of the columnar cells, but of about the same 
size. They each possess one very large, centrally placed nucleolus, whose 
diameter equals and sometimes exceeds one third that of the nucleus, and 
whose outline is often somewhat stellate. Outside of the nucleus in the 
cell body there are fewer and fewer vacuoles as we pass from the tip, but 
the plasma is still coarsely granular, and here, as before, these stained 
granules surround the nucleus. It is now the regions between cells 
rather than those at the inner and outer ends which remain unstained, 
so that the cells are separated from one another by light spaces. 
The mesodermal layer becomes somewhat thinner than at the tip, that 
is to say, its cells are flattened. The nuclei are elongated in the axis of 
the branch, and average about 4p by 2.2 p. They possess one spheri- 
cal nucleolus, whose diameter is about two thirds of the minor axis of 
the nucleus. Small, clear vacuoles often with highly refractive spherical 
bodies are abundant in the cell protoplasm, which stains as a whole less 
deeply than does the ectoderm. Such highly vacuolated elements will 
be called reticulated cells. 
If we study the gemmiparous zone at a stage considerably earlier than 
that shown in Figure 14, in fact at a stage in which a polypide is about to 
arise, we find an appearance of the layers represented by Plate I. Fig. 3. 
In such a region the ectoderm consists of cuboid cells about 7p high by 
6.5 abroad. The nuclei are large, nearly spherical, and vary in size from 
3.5t06.0p. The largest nuclei are those in the region from which a bud 
is about to arise (ex.). One in this region (to the right of ex.) is 6.5 u 
by 6.0 p in diameter, with a nearly spherical, eccentrically placed nucleo- 
lus of about 3.0 p in diameter. This nucleus is the largest which I have 
found in the whole tissue of Paludicella, and the same is true of the nucle- 
olus. From the examination of many regions from which buds are about 
to arise, I can assert that such regions always, in Paludicella, possess large 
nuclei and large deeply staining nucleoli, I shall have occasion to de- 
scribe similar conditions elsewhere, and to point out the probable signifi- 
sance of these facts. The cell body possesses a highly granular, deeply 
