HYDROZOA. 
53 
efficiency even on old dried specimens. The degenerate dactylozooids Case 4 
have a number of capitate tentacles, while the gastrozooids have only 
a whorl of four (Fig. 16). 
In 1891 Prof. Hickson discovered the male, and in 1898 the 
female Medusa (Fig. 17) of Milleporci in small capsules, which, when 
occurring near the surface, form rounded swellings (ampullae). 
Latterly, Mr. Duerden has seen the living Medusae in his aquarium 
at Jamaica. This tiny Medusa is only about ^ inch in diameter ; 
its cavity is nearly filled up by the large manubrium containing the 
eggs. The umbrella is devoid of canals, tentacles, and sense-organs, 
but is provided with batteries of thread- 
cells ; and usually no mouth can be 
seen at the end of the manubrium. 
The little creature, however, is able to 
swim away with its heavy burden of 
eggs from the parent colony ; having 
deposited the eggs, it shrivels up. 
Stylasterid^:. In this family the 
dactylozooids are without tentacles, aud 
one or both kinds of zooids are supported 
in their calicles by a calcareous style. 
There are several genera in this family. 
In Stylaster the pores are arranged 
in “ cyclo-systems ” — a circle of dacty- 
lopores surrounding a central gastropore. each with a central gastropore. 
A cyclo-system presents a deceptive g™" n ) atu,al size '> ( After 
resemblance to the calicle of an ordinary 
coral ; in the latter the calicle contains one coral polyp, but in the 
cyclo-system there are a dozen or more degenerate individuals sur- 
rounding a central individual ; the dactylozooids were formerly 
supposed to be the tentacles of the central zooid. The generative 
buds, which are situated in the often numerous swellings or ampullae, 
never become free Medusae. 
The Stylasters are remarkable for the elegance and beauty of 
their arborescent fan-shaped forms (Fig. 14) and their exquisite 
colouring. Several specimens of Stylaster roseus from off a cable 
from the West Indies show considerable variation in colour, being 
white, rose-pink, and salmon-coloured. The cyclo-systems regularly 
alternate on the sides of the slender branches. 
From “Encyclopaedia Britannica.” 
