LIFE-HISTORY OF MELICERTIDIUM 345 
I agree with Romanes’ opinion (9, p. 527) that the © radiating 
lines’ referred to under Melicertidium (medusa) above are 
bands of muscle fibres, and not of nematocysts as is thought 
by Browne (4, p. 764) and others. 
Additional instances in which theca-less hydroids have been 
reared from Leptomedusae are recorded by Claus (5), Metchni- 
koff (8), and Brooks (2). ‘Che medusae concerned belong to 
the genus Hutima (McCrady), the species being HKutima 
campanulata (Claus), Octorchis gegenbauri(Haeckel), 
in the first two cases, and Kutima mira (McCrady) in the 
third. Eutima differs from Melicertum and Melicertidium, 
among other things, in having marginal lithocysts, and in 
having the stomach mounted on a long peduncle. In the 
hydroid of E. campanulata, deseribed by Claus and 
named by him Campanopsis, the tentacles are up to twenty- 
four in number and are united at their bases by a membrane. 
A theca is entirely absent, and the young medusae are formed 
near the middle of the hydranth body. Brooks (2) describes 
the hydroid of H. mira as small, Perigonimus-like, with 
eight tentacles united at their bases by a membrane. 
EK. Stechow (10) has described a theca-less hydroid, with 
short hydrocaulus having definitely ringed perisare, with 
hydrorhizae forming a network, and with fourteen to eighteen 
tentacles which were not, so far as could be made out in the 
preserved material, united at their bases by a membrane. 
The specimens were in a tube left by a former assistant at 
Munich and were labelled ‘ Polyp of Octorehis’. Stechow 
names it Campanopsis dubia and considers the medusa 
to have been an Octorchis Hutima. 
On the whole, the life-history of Melicertidium: supports 
the generally-accepted view that Leptomedusan hydroids are 
derived from Anthomedusans. The hydroid is theca-less, the 
inedusa is deep and has no lithocysts or ectodermal ocelli, and 
though the gonads are on the eight radial canals in the adult, 
the mode of development of the second four radial canals by 
outgrowths from the stomach makes it clearly possible that 
ontogenetically or phylogenetically the gonad tissue of the 
