No. 3.-] DEVELOPMENT OF MARINE SPONGES. a7 7 
the amoeboids. In Esperella and the other sponges only a 
portion are so absorbed, while the remainder throw out proc- 
esses and unite with one another and the now multinucleate 
amoeboids, to form a syncitial net-work. In the development 
of a chamber several of the multinucleate masses approach 
one another and form a continuous wall round a central space. 
The space becomes the cavity of the chamber, round which 
the nuclei of the absorbed ciliated cells arrange themselves in 
a regular fashion, while the nucleus of the amoeboid sur- 
rounded by protoplasm escapes from the periphery of the 
chamber anlage, and becomes a wandering cell of the meso- 
derm. The ciliated cells not associated with the amoeboids, 
but which are merely part of the syncitium, unite in the same 
manner and form chambers.” 
The multinucleate formative cells I have described evidently 
correspond to Delage’s multinucleate amoeboids. But while 
Delage agrees with Gétte and myself (35, and ante) in regard- 
ing the smaller peripheral bodies as nuclei, he differs com- 
pletely in his explanation of their origin ——I regard them as 
derived from the central larger nucleus of the cell. 
Delage’s observation that chambers arise from the fusion of 
several multinucleate groups, corroborates the account I have 
given of one of the methods of chamber formation (35, and 
ante, p. 312), though, as before said, we differ greatly in our 
views of the ultimate origin of such groups. But on the other 
hand I have repeatedly observed that chambers may also be 
formed by formative (amoeboid) cells which group themselves 
in hollow spheres. Some of these cells may contain but a 
single nucleus, while others contain more. Observations such 
as this would seem to disprove Delage’s thesis that the col- 
lared cells are the immigrated ciliated cells of the larva. 
Canal Epithelium. — Delage, like myself, finds that the 
canals arise independently of one another, as irregular spaces 
in the inner mass, that they gradually become lined with a 
definite epithelium and unite with one another and with the 
chambers to form a connected system. Regarding the origin 
of the canal epithelium, however, Delage entertains widely 
different views from my own. His account is as follows: 
