CORAL AND CORAL MAKERS. 21 
them, the number of tentacles and interior septa a multiple of 
six. The name Actinza is from the Greek for ray. 
II. CyatuopHyLioip Potyps.—Nike the Actinoids in tenta- 
cles and interior structure, except that the number of tentacles 
and interior septa is a multiple of four. Ludwig and De 
Pourtales state that the number in the earliest young state is 
siz, and that therefore the fundamental ratio is the same as in 
the Actinoids; and that they pass from this ratio by develop- 
ments of tentacles and septa more rapidly on one side than the 
opposite, and in such a manner that the number becomes after 
the first stage a multiple of four. The Cyathophylloid polyps 
hence combine this characteristic of the Actinoids with one 
feature of the Alcyonoids. The Cyathophylloids were the ear- 
liest of polyps, and the most abundant species in Paleozoic 
time. 
III. Aucyonorw Potyrs.—Having eight fringed tentacles, 
and other characters mentioned beyond; as the Gorgoniz and 
Alcyonia. 
I -ACTINOID: POLYPS: 
The highest of Actinoid Polyps are those of the Actinra 
TRIBE—the species that secrete no coral to clog vital action 
and.prevent all locomotion. ‘The details of structure may be 
best described from the Actinia or Sea-anemone, and after-— 
ward the distinguishing characters of the coral-making polyps 
may be mentioned. In external aspect and in internal charac- 
ters all are essentially identical. 
1. NON-CORAL-MAKING POLYPS. 
As the colored figures on Plate II., and also the following. 
show, the external parts of an Actinia are —a subcylindrical 
