ACTINOZOA. 91 
Crass II.—THE ACTINOZOA. 
Calenterates with a digestive sac partially free from the body-cavity opens 
tng into it below and held in place by six or eight mesenteries radiating from 
the digestive cavity and dividing the perivisceral space into chambers. Mouth 
surrounded with a circle of tentacles, which are hollow, communicating dis 
rectly with the perivisceral chambers. A slightly marked bilateral symmetry. 
To the edges of the mesenteries (usually the free ones) are attached the repro- 
ductive glands, both male and female, or of one sex alone ; also the craspeda, 
or mesenterial filaments, which contain a large number of lasso-cells. Body 
either entirely fleshy, or secreting a calcareous or horny corai-stock, and 
when the species 7s social connected by a ceenenchyme. In some forms (sea- 
pens) the entire colony capable of limited locomotion. No well-marked 
nervous system, but a plexus of fusiform ganglionic cells connected by nerve- 
fibres in the base of Actinians. Reproduction by self: division, gemmation, 
or by ova, the sexes being separate or united in the same individual ; the 
young undergoing a morula and gastrula condition, and then becoming 
fixed. 
Order 1. Zoantharia.—Mesenteries and tentacles usually six or in mul- 
tiples of six, corallum with calcareous septa. Mesenterial fila- 
ments abundantly developed (Astrea, Madrepora, Actinia). 
Order 2. Aleyonaria.—Mesenteries and tentacles always eight in num- 
ber. Coral-stock without true septa. Mesenterial fila- 
ments not usually numerous. Corallum usually horny, and 
the whole colony in the Pennatulacea capable of locomo- 
tion (Alcyonium, Gorgonia, Pennatula, Renilla). 
View oF THE CLASSIFICATION OF THE ACTINOZOA, 
Alcyonaria. 
(Alcyonium.) 
Zoantharia, 
(Actinia.) 
— 
ACTINOZOA. 
Laboratory Work.—Verrill has preserved Actinie completely ex- 
panded by slowly adding a saturated solution of picric acid to a smalt 
quantity of sea-water in which they had expanded. When dead they 
should be transferred to a pure saturated solution of the acid, and 
allowed to remain for from one to three hours, according to size, etc. 
They should then be placed in alcohol, which should after a day or two 
be renewed. Thus hardened they can be cut into sections. Corais 
can be studied by grinding or sawing sections, and, if desirable, treated 
as in the case of the corallum of the Millepores. 
