2 
CRETACEOUS CORALS OR ANTUOZOA 
name Authozoa, Polypi, or Corals, is restricted, and those in which the month 
directly communicates with the general cavity of the body, and which, according 
to Agassiz, have in late years been transferred to the Ilydrozoa, — namely, the so- 
called Podactinaires or Lucernariism, together with the Madreporaria tahulata and 
rugosa of Milne-Edwards and Ilaime. 
The general cavity of the body is internally in its entire extent instructed with 
cilia ; the chyliis is formed in, or passes from, the so-called stomach into it, and its 
circulation, as well as that of the water for purposes of respiration, is chiefly pro- 
duced through these cilia, while the tentacles act not only as prehensile organs for 
obtaining food, hut also for producing a current of Avatcr leading to and from the 
mouth. This very simple arrangement dispenses with the necessity of all other 
special organs or vessels for digestion or respiration. Equally so a nervous 
system, or special organs of sense, are absent, but the soft parts of the body, and 
particularly the tentacles, are sensitive both to touch and to the light. Some 
naturalists believe that the presence of peculiar branched cells in the oral disc 
indicates the rudiments of a nervous system. In some of the Actiniacea there are 
peculiar thread-like organs, the so-called craspeda, present between the septa, and 
these appear to act, at least in some cases, as secretionary organs and assist in 
digestion. Resides there are in some Authozoa other organs for the defence of the 
animals, the so-called nettle threads or acontia, which are emissiblc and secrete a 
sharp fluid in the cnidic or nettle cells.* 
The sexes are, as a rule, distinct, either in the same or in different individuums, 
and in some cases of the compound corals one sex is said to be restricted to a single 
colony. The progeny leaves the mother either in the form of fertile ova, or as a 
developed Anthozoon with tentacles. The young, when it leaves the ovum, swims 
about with a row of cilia, gradually the body curves, forms an internal cavity, the 
rudiments of tentacles appear, and the young Anthozoon becomes sessile. In 
other cases propagation takes place by budding, or gemmation, and thus compound 
colonies are formed. 
The body of the Anthozoon is composed of an external and an internal 
cilia-bearing skin, each consisting of several layers. Between them is the mus- 
cular system developed, the several layei’s being composed of vertical or longitudinal 
and of concentric fibres. All these soft parts appear to be in certain cases capable 
of secreting solid particles of various shapes, the so-called sclerites or scleroder- 
mites, which either remain isolated in the fleshy or dermal mass, or they coalesce 
to a more or less solid, reticulated or porose skeleton, which was called sclerenclujvia 
by Messrs. Milne-Edwards and Ilaime. 
The calcification, or rather sclei'ification, ju’Ogresses in somewhat different 
manner in A'arious forms. In some it takes place only at the basis of the single or 
compound individuum, and continues to grow and branch as a kind of axis, 
* Compare my note on Sagariia in Journ. A. S. B. for 18(39, vol. xxxviii, pt. ii, pp. 43 and 50. 
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