Cotylorhiza and Rhizostoma. 181 
apparatus has been fully described by me in the work above 
cited ; and here I venture only to call attention particularly to 
the development of the nematophores, which also stand in 
an important relation to the establishment of points of amalga- 
mation in the progress of the buccal arms, which are greatly 
enlarging and forming secondary infundibuliform folds. 
In general therefore it appears (and the same may also 
recur in Rhizostoma and all Rhizostomez) that the early ap- 
pearance of the buccal tentacles in the Cannostomous stage ¢s 
the primary process superinducing rhizostomism, then fol- 
lowed by the pecuiiar form of the four arms with their ex- 
tended distal margin, and then paired foldings of the brachial 
processes. Krom these stages onwards the development of 
rhizostomism depends essentially upon the continued folding 
of the surfaces of the arms, and their margins beset with ten- 
tacles, as I have already described in detail (C. Claus, Z. c. 
p: 52 &e.). 
As regards the yellowish-brown corpuscles which occur in 
great quantity in the entoderm of the larve of Cotylorhiza, 
they belong undoubtedly to the category of the plant-cells 
which vegetate symbiotically in so many of the lower organ- 
isms, first recognized as such by Cienkowski*, and_subse- 
quently distinguished by R. Brandt} as zoochlorelle and 
zooxanthelle. In Cotylorhiza they were detected some years 
ago by Hamannf, but erroneously interpreted as unicellular 
glands with a difficultly recognizable aperture, until soon 
afterwards Patrick Geddes§ first demonstrated their true 
nature. 
These chlorophyll corpuscles lie here and there singly, but 
generally in groups, in the cells of the entoderm, and project 
as globular or racemose balls into the jelly. Probably they 
have originated as products of continued division from a single 
cell; and, in point of fact, one meets with all transitions down 
to the bisection of the cell. I have never seen the zoo- 
xanthelle completely separated from their union with the ento- 
derm, although it is not improbable in itself that they might 
be transferred in‘o the jelly by entodermal cells which have 
* Cienkowski, “ Ueber Schwirmerbildung bei Radiolarien,” in Archiv 
fiir mikr. Anat. 1871. 
+ K. Brandt, “ Ueber das Zusammenleben von Algen und Thieren,” in 
Biolog. Centralbl. 1881, no. 17; and also Geza Entz, did. 1882, 
no, 21. 
{ O. Hamann, “ Die Mundarme der Rhizostomen,” in Jenaische naturw. 
Zeitschr. Bd. xy. 1851. This author has lately recognized the error of 
his interpretation and retracted it. 
§ Patrick Geddes, “On the Nature and Functions of the ‘ Yellow Cells’ 
of Radiolarians and Ceelenterates,” in Proc. Roy, Soc. Edinb, 1882. 
