230 
POPULAR SCIENCE REVIEW. 
Between the fixed reproductive bud, which in some genera 
originates and matures the ova, and the vagrant members that 
we have just described, a series of transitional forms is met 
with, uniting the one structurally with the other. In some 
cases a near approach is made to the medusiform structure, and 
the sexual zooid appears to be on the high road to independent 
existence, but development is arrested, and it remains attached 
to the parent stock until the embryos are liberated. Occasion- 
ally it even passes beyond the orifice of the capsule (Plate 
XLV. fig. lee), and hanging there like a ripe seed-vessel, dis- 
charges its contents and then withers away. 
Most beautiful in form, colour, and motion are these floating 
polypites — these quasi flower-buds and seed-bearers of the 
plant-like zoophyte ! The umbrella or swimming organ, often 
of most exquisite shape, is now clear as crystal, and now deli- 
cately tinted ; the pendent body within is frequently adorned 
with the gayest colours; the margin of the bell is fringed with 
the tentacles, which hang in spiral coils or stream through the 
water in graceful curves : and the whole bubble-like structure 
floats dreamily, like a balloon suspended in mid-air, or is borne 
rapidly onward by the pulsations of the contractile disc. The 
contrast is complete between its habit of life and that of its 
sedentary kindred. 
The medusoids (to use a common but somewhat misleading 
term) often increase greatly in size and complexity of structure 
after their liberation from the colony, changing their aspect so 
entirely that it is difficult to identify them in their early and 
later stages; they bud off, like the common Hydra, large num- 
bers of young, which become detached ; and finally they elaborate 
the ova and spermatozoa, and having scattered the seed of new 
generations, they perish. Like the flower of the plant, they 
are in all probability comparatively short-lived. Their num- 
bers are immense; at certain seasons of the year they swarm 
near the surface of the sea, and contribute in no slight degree 
to produce the beautiful phenomena of phosphorescence. 
The ova are developed into somewhat elongate ciliated embryos 
(planulce) (Plate XLV. fig. 1 e'e'), which on escaping from 
the ovary enjoy a term of free existence, and then pass through 
the course of development described on a previous page, and 
give rise to the tree-like colony. They remind us of the winged 
seeds of the plant. 
Amongst the family of the Sertulai'iidce, and some other 
sections of the Thecaphora, the reproductive buds are always 
fixed-, but in the beautiful group of the Campanulariidcc (vide 
Plate XLV.), reproduction by free zooids is of common occur- 
rence. 
After tin's rapid sketch of the life-history of the zoophyte, we 
have only space to refer ver}' briefly to a few of the forms most 
