711 
celerated development of the gelatinous umbrella, and here to we 
have four radially arranged primary tentacles. 
The first hydranth of Hydractinia is almost exactly like Hamann’s 
Podocoryne. It has at first four primary radial tentacles, one at each 
angle of the mouth: and four smaller inter-radials afterwards make 
their appearance. 
In all these cases there are four radii. But in Stomatoca and in 
Tubularia cristata there are five, as in Eutima. 
In the hydranth (Perigonimus) of Stomatoca apicata (MeCr.) 
even when fully grown, there are usually five large radials, and five 
smaller interradials. It is true that the number ten is not universal, 
but it is constant enough to show that it is the typical number, and 
this is true also of the actinula of Tubularia cristata, in which the lips 
of the five radials are turned forwards, and the lips of the five smaller 
interradials are turned backwards or towards the aboral end of the 
body. In some actinulae there are only eight or nine tentacles, and in 
others eleven or twelve, but ten is the typical number. 
In a Beaufort Podocoryne which is probably the larva of Dysmor- 
phosa fulgurans the tentacles are usually in fives. 
We therefore have radial symmetry with four parameres in 
Podocoryne Heckela, 
Hydractinia (young hydranth), 
Cunina octonaria (young larva), 
Polyxenia leucostyla (young larva), 
Arginopsis Mediterranea (young larva), 
Liriope (egg, embryo) 
and radial symmetry with five parameres in 
Podocoryne (Dysmorphosa) (mature hydranth), 
Eutima mira (young hydranth), 
Perigonimus (Stomatoca) apicata (mature hydranth), 
Tubularia cristata (Actinula). 
In a Beaufort Sertularia, Dinamena bilateralis, the tentacles 
exhibit marked bilateral symmetry. They are about twenty-two in 
number, and are arranged in an elipse, with the short axis in the plane 
of the stem, and the long axis at right angles to the stem. There is a 
siugle tentacle, shorter than any of the others, at each end of the long 
axis, and on each side of this they gradually increase in size towards 
the poles of the short axis, where they are largest. This bilateral sym- 
metry is undoubtedly induced, like the symmetry of the hydrothecae, 
by the bilateral arrangement upon the stem, but it is interesting to 
note that it is not general among the Sertularia, 
Baltimore, October 3th 1884. 
