310 WILSON. [VoL IX, 
ture of about the size and of the same character as a pore. 
Such peripheral foramina (/. for.) are not common in Espe- 
rella, and seem to have no function. 
Flagellated Chambers. — After the larva attaches, Pl. XVII, 
Figs. 36, 37, 38, it is, as has been said, largely composed of 
formative cells. Other smaller cells, bipolar or otherwise 
branched, are scattered amongst them. Moreover, all the mes- 
entoderm cells are united into a network, Pl. XVII, Figs. 30, 
42. The formative cells, many of them at any rate, are multinu- 
cleate. In Pl. XVII, Fig. 46, a group of formative cells is shown, 
some of which are multinucleate. These possess, besides the 
central larger nucleus with its nuclear membrane and chromatin 
mass, one or more smaller peripheral nuclei, each having its 
chromatin mass with nucleoplasm and surrounding membrane. 
The peripheral nuclei at first sight look like mere chromatin 
spots, but more careful study satisfied me they were surrounded 
by nucleoplasm and a membrane. There are, however, scat- 
tered about in the cell protoplasm other bodies which stain 
like chromatin balls, but which are in all probability yolk gran- 
ules. Two of these are shown in the lowermost cell of PI. 
XVII, Fig. 46. 
In Spongilla, Gotte (6) has described multinucleate cells, 
which break up by a process analogous to budding, and form 
cell-croups which give rise to the flagellated chambers. The 
multinucleate cells are derived from mesoderm cells containing 
a nucleus and large yolk granules, the yolk granules becoming 
transformed into nuclei! Maas (14) has studied the same 
cells (‘Dotterzellen”’) in Spongilla, using a differential stain 
(Lyons blue and carmine, or malachite green and carmine). 
He thinks that the cells in question contain only a single 
nucleus, together with a number of yolk granules of varying 
size. The nucleus stains red, the yolk granules blue. Maas 
does not believe that these cells are concerned in the forma- 
tion of the chambers, but describes the latter arising as 
diverticula from a main entodermic cavity. Maas has also 
studied (16) what I have called “formative cells” in Esperia, 
and does not believe they are multinucleate. The bodies 
which I regard as small nuclei peripherally placed, he thinks 
