Observations on British Zoophytes, 
43 
On examining a specimen of Stomobracbium last summer, 
which had been recently fed on the white part of an oyster, 
I noticed (fig. 1 a a a) a retiform system of fine canals, 
which permeated the muscular web of the sub-umbrella, and 
was altogether distinct from the eight large lateral canals 
which carried the ovarian bands. This canal system con- 
sisted of from three to five fine tubes, which sprung from 
the upper part of the peduncle, between each of the lateral 
canals, and passed outwards and downwards as a rarely anas- 
tomosing network, to join the circular canal bordering the 
mouth of the bell. No branches ^from it joined the lateral 
canals, as the latter were bordered on each side by the long 
ovarian bands. Throughout the whole supplementary system 
in water recently brought from the sea. It must be slowly filtered through 
blotting-paper into a glass vessel capable of containing not less than three 
or four gallons, iu which are placed a few fronds of Chondrus crispus, Entero- 
morpha or Ulva. A few Medusae only should be placed in the vessel, and fed 
with very small pieces of mussel. 
As soon as the planulse appear they should be removed with a dipping- 
tube into a round glass shade inverted and filled with filtered sea-water from 
the larger vessel, to which a few drops of mussel-juice must be added daily, 
until it appears crowded with minute protozoa. The internal surface of the 
glass, and especially the surface of the water, should be examined daily from 
without with an inch lens, and as soon as each planula adheres to the inside 
of the glass, a thin cover of microscopic glass should be attached externally 
over its site with an interposed drop of glycerine, to ensure a flat surface, 
and the microscope, placed on a proper support, should be brought up to 
it. The light, the quantity of which must be regulated by a diaphragm 
of black paper, should be reflected from a plane mirror, and carefully adjusted 
to pass directly in the axis of the tube of the microscope. By this means 
the whole process of the development of the planula into the hydroid 
zoophyte, with the successive budding of the polyps, may be seen in a 
very beautiful manner. This process is carried out in a period varying 
with the genus from which the planula is derived. Thus, in Sertularia 
pumila and Campanularia dichotoma, the first young polyp is complete in 
a few hours ; while in Hydractinia and Equorea, our patience is tried 
for several weeks ere the same event occurs. The planula of the Stegan- 
opthalmata, such as Chrysaora, Cyanea, and Aurelia, may be removed from 
the ovaries or marsupial sacs of the Medusae as they lie exposed on the sea 
shore, and rarely fail to become developed into polyps or Ephyrse, In this 
phase of their development they remain for many years, if well fed and kept 
in a darkened place, and multiply rapidly by gemmation. They may, how- 
ever, be forced to assume their medusoid phase, by exposing them, without food^ 
in a small quantity of sea-water, to direct sunlight. 
