CCELENTERATA. 
623 
the simple cellular connective tissue of the Hydrozoa^ and that 
betweeik the two only the same trifling difference exists that will 
be found in other places between old and young cartilage. The 
different forms of gelatinous connective tissue are described as 
met with in part of the Medusm phanerocarpse, in the Cteno- 
phora^ in part of the Alcyonaria, and in part of the Zoantharia. 
Fibrous connective tissue is described as found among the 
Pennatulidse, in some of the Alcyonaria (Spoggodes and Ammo- 
tiled) and among some of the Aptinidse {Actinia and Edwardsia). 
W. C. M^^Intosii (Proc. Roy. Soc. Edinb. vol. v. p. 602) gives a 
list of thirteen species of Actinozoa and Hydrezoa met with at 
North Uist^ Outer Hebrides. 
ACTINOZOA. 
In treating of the hardened connective tissue of the Coelen- 
terata, Kolliker (/. c. p. 1 1 7) remarks that by several writers the 
skeleton of the Actinozoa is treated of as if one portion was 
excreted by the outer layer of the body (foot secretion, Dana), 
and another was a hardening of the deeper layers (tissue sfecre- 
tion, Dana). To the former were referred the horny and calca- 
reous axes of Gorgoniaj Isis, Cor allium, and Pennatulidcs, and to 
the latter the spicula of the Alcyonaria, the tubes of Tubipora, 
and the skeleton of the Zoantharia. This, however, is simply 
an hypothesis, the fallacy of which has been shown by recent 
researches. The following are the forms of hardened connective 
tissue met with in this group : — 
I. Hard structures, which are substantially made up of isolated small por- 
tions of a determined form (such as the isolated calcareous bodies of 
Alc 5 ’^onid 8 e, &c.). 
II. Hard structmes, which form coherent deposits (die zusammenhan- 
gende Ablagerungen darstellen). Of these one finds : — 
1. Hard bodies which exist as isolated or amalgamated calcareous 
bodies in combination with a horiiy or chalky interstitial substance, ' 
or alone as a confluent calcareous substance. (Axis of Melithseaceae, 
Sclerogorgiacea3, and Corallinse.) 
2. Lamellated structures, which, for aught it seems, are formed as secre- 
tions, and which, when calcified, leave, after the removal of the 
salts, an organic remainder of the same form. To this section 
belong : — 
• a. The horny axis of Gorgonidae and Antipathidoe and the horny in- 
terstitial joints of Isis. 
h. The more or less calcified lamelloso axes of the Gorgonidao {Primnoa, 
Plomurclla., Isis, »fec.) and Pennatiilid.'o. 
3. Crystalline structure, which seems to increase through a deposit of 
chalk in a preexisting tissue, but after the removal of all the salts 
leaves an almost inappreciable organic residue. Here are included : — 
a. The gi’eater number of those with merely superficial skeletons 
{Tubipora). 
