LITERATURE OF THE SUB-KINGDOM CffiLENTERATA. LSI 



The class Hydrozoa (i, e. animals whose type is the genus Hydra) 

 will include seven orders, viz. — 



Order 1. Hydridje (= Hydrina of Ehrenbcrg). — Hydra itself 

 is the sole representative of this division. 



Order 2. Coryxtd.e or Tubularid.e (= Tubularina of Ehrcn- 

 berg). — Here are placed those fixed Hydrozoa which want "hydro- 

 thecae," or polype cells, the distinctive structural feature of 



Order o. Sebtttlabijxs! (= Sertularina of Ehrenberg). 



Order 4. CALYCornoitiDiE. — In this order, the name of which 

 was first suggested byLeuckart, are placed such of the Siphonophora 

 as do not possess an air-vesicle and float, the presence of which dis- 

 tinguishes the members of the next group, 



Order 5. Physopiioridj;. 



Order 6. Medusid.e. — Such CryptocarpaB (for example, Cunina)^ 

 as appear to be the direct offspring of forms resembling themselves, 

 together with many others whose genesis is unknown — i. e. which 

 have not yet been proved to be merely the free reproductive buds of 

 other Hydrozoa — may for the present find their best place in this 

 order. 



Order 7. Lucerxaridje. — The family Lucernariadre of Johnston, 

 in addition to the Phanerocarpa? of Eschscholtz, belongs, as above 

 stated, to this group. 



The second class, Actinozoa (i. e. animals typified by Actinia), 

 divides itself into four orders : — 



Order 1. Zoaxtiiaria. — This group includes all the Polypes so 

 designated by Milne Edwards, save those wdiich are placed in the 

 following order. 



Order 2. Eugosa. — The four extinct families of Sclerodermic 

 Corals, associated under this name by Milne Edwards with the 

 Zoantharia proper, may on just grounds be elevated to the rank of a 

 separate order, distinguished by the tetrameral arrangement of their 

 (in general well developed) septal system from the members of the 

 preceding division, whose septa and tentacles are usually some mul- 

 tiple of five or six. In the numerical proportion of their parts, there- 

 fore, the Eugosa differ from the Zoantharia, and resemble the two 

 remaining orders of Actinozoa. 



Order 3. Alcyoxaria. — A sharply- defined group, the pofypes of 

 which always present eight pinnate tentacnla. 



Order 4. Ctexophora. 



Sub-kingdom CCELENTEEATA. 



Animals whose alimentary canal freely communicates with the 

 somatic cavity. 



Substance of the body made up of two foundation membranes, 



65 For a very recent addition to our knowledge of the life-history of this genus, 

 see Fritz Miiller on Cunina Eollikeri, n. s., inWiegmann's Arch. 1861, p. 42. 

 VOL. I. — X. H. R. 3 K 



