Cotylorhiza and Rhizostoma. 177 
with zoochlorelle, a peculiarity which immediately catches the 
eye as influencing the coloration and marking. 
As for a long time | could not sueceed, notwithstanding 
many endeavours, in obtaining sexually mature Cotylorhize 
at the period of egg-laying, and consequently in rearing 
Ephyre, I attempted to get possession of them in another way, 
namely by pelagic fishing. For several years larve of Rhizo- 
stoma and Cotylorhiza were regularly captured, especially in 
August, which, being already in stages of more or less ad- 
vanced development, could be easily determined as belonging 
to those two genera. I was therefore enabled some time since 
to publish a tolerably detailed account of the metamorphosis of 
these larve—which were already provided with intermediate 
marginal lobes, bifurcate buccal arms, and traces of the vas- 
cular net—into the perfect Lhizostoma- and Cotylorhiza-form*. 
The Ephyre, however, were not to be obtained, and conse- 
quently an important part of the transformation, namely that 
of the Ephyre into the four-armed, and of the latter into the 
eight-armed form, remained unknown. ‘The circumstances 
through which the important peculiarity of rhizostomism is 
brought about and conditioned consequently were still to be 
ascertained. It was only in the summer of the present year 
that our zealous and able seaman Kossel chanced to fall in, on 
the 14th, 17th, and 18th July, with great swarms of Cotylo- 
rhiza-larve, in which were included all those young states 
which had hitherto been sought in vain. 
The swarms, as Dr. E. Graetfe informs me, were driven 
together with masses of Zostera and of Sargassum covered 
with Hydroid polyparies, in the middle of the Gulf of Trieste 
between Barcola and the lighthouse, and must probably have 
been brought up by strong currents from the southern parts 
of the Adriatic. 
Now it appeared that the same Ephyra had already once 
before been observed singly by me, and determined quite cor- 
rectly from the nature of the entoderm, which was filled with 
algal cells, as probably belonging to Cotylorhizat. Of course 
absolute certainty could only be arrived at by the demonstra- 
tion of the intermediate steps to the undoubted Cotylorhiza, 
which was now furnished by the discovery of this swarm in 
all stages of transition. The circumstance that the entoder- 
mal coat of the gastral cavity and vascular canals was filled, 
although imperfectly, with zoochlorelle, might probably indi- 
* ©. Claus, ‘Untersuchungen tiber Organisation und Entwicklung der 
Medusen’ (with twenty plates), Prague and Leipzig, pp. 44-06, 
+ C. Claus, /. ce, p. 54. 
