ACTINOZOA. 91 



Class H.— THE ACTINOZOA. 



CcAenteratea vyith a digestive sacpartiaUi/ free from the hody-cavity open- 

 ing into it below and held in place by six or eight mesenteries radiating from 

 the digestive cavity and dividing the perivisceral space into chmnbers. Mouth 

 surrounded mth a cii cle of tentacles, which are hallow, communicating di- 

 rectly with the perivisceral chambers. A slighdy marked bilateral symmetry. 

 To the edges oftlie mesenteries {usually the free ones) are attached the repro- 

 ductive glands, both mule and female, or of one sex alone ; also the craspeda, 

 or mesenterial JUameht.i, which contain a large number of lasso-cells. Body 

 ■either entirely fleshy, or secreting a calcarsous <w homy coral-stock, and 

 wlien the species is social connected by a cancTichyTne. In some forms {sea- 

 J)e7is) the entire colony capable of limited locomotion. No weOHnarked 

 nervous system, but aplexus of fusiform ganglionic cdls connected by nerve- 

 fibres in tlie base of Actinians. Reproduction by self division, gemmation, 

 or by ova, tlie sexes bemg separate or united in tlie same individual ; the 

 3joung undergoing a morula, and gastrula condition, and then becoming 

 faed. 



Order 1. Zoantharia. — Mesenteries and tentacles usually six or in mul- 

 tiples of six, corallum with calcareous septa. Mesenterial fila- 

 ments abundantly developed (Astraea, Madrepoia, Actinia). 



Oj'oer 2. .^fcj^oraana.— Mesenteries and tentacles always eight in num- 

 ber. Coral-stock without true septa. Mesenterial fila- 

 ments not usually numerous Corallum usually homy, and 

 the whole colony in the Pennatulacea capable of locomo- 

 tion (Alcyonium, Gorgonia, Pennatula, Eenilla). 



View op the Classification op the Aottnozoa. 



Alcyonaria. 

 (Alcyoijiiuin.) 

 Zoanlhnrin. 

 (Actinia.) 



ACTINOZOA. 



Lahvraiory Work. — ^Verrill has preserved Actinise completely ex- 

 panded by slowly adding a saturated solution of picric acid to a small 

 -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 section.s. Corals 

 can be studied by grinding or sawing sections, and, if desirable, treated 

 ms in the case of the corallum of the Millepores. 



