368 
PROFESSOR E. RAY LANKESTER. 
cisely with the Trachomedusse, such as Ehopalonema, described 
by the Ilertwigs. It appears that in Ehopalonema and other 
Trachomedusse, the marginal body originates as a small 
tentacle-like outgrowth with endodermal axis. Whilst the 
endodermal axis undergoes modifications, an ectodermal up- 
growth (of the abumbral velar surface) occurs all round the 
little tentacle so as to form a sort of investing vesicle, which at 
first is open, but in the course of development closes up. The 
^ little tentacle is thus enclosed in a spherical sac or capsule. 
Precisely the same history attaches to the tentacle-like com- 
mencement of the refringent body of Limnocodium, excepting 
that the capsule commences somewhat early, and that the whole 
structure, both tentacle-body and capsule, instead of standing 
out freely on the abumbral surface of the velar insertion, keeps 
a special course of direction of growth, creeping so to speak 
between the two layers of the velum instead of pushing out- 
wards at right angles to the abumbral surface. 
There can, it seems to me, be no doubt that the refringent 
body of Limnocodium is identical with the free auditory bulbs” 
(freie Horkolbchen) of Trachyline Medusae, in which phase the 
so called auditory organ of Trachomedusae makes its first ap- 
pearance. The tubular capsules” or “ velar centrifugal canals,” 
which enclose the refringent bulbs of Limnocodium, are iden- 
tical with the at first open and subsequently closed auditory sacs 
of ectodermal origin, which grow up around the Horkolbchen 
of Trachynemidae, Olindiadae, and Geryonidae. 
I have observed the development of true tentacles in the new 
Medusa, and may state that in them the endodermal axis at 
once begins to assume its special character, wLich prevents any 
possibility of confusion (apart from their different positions) 
between the true tentacle and the tentacular auditory ” 
bulb. 
Until it is shown (as it appears to me very possibly may 
some day be shown) that some Leptomedusse have their marginal 
bodies formed by modified tentacles, as in Trachomedusse and 
Narcomedusse, and not purely and simply from ectodermal cysts, 
as the Hertwigs have described, the features wdiich I have 
shown to characterise the development and essential structure 
of the marginal bodies of Limnocodium will render it necessary, 
even apart from those features of the tentacles and marginal 
ring above described, to associate that form, not with Lepto- 
medusse, but with the Trachomedusse, as I pointed out when I 
gave to it the name Craspedacustes. 
Embryonic condition of Limnocodium . — Not the least astonish- 
ing fact about the new fresh-water Medusa is the immense pre- 
ponderance of males. Among more than fifty specimens wdiich 
