358 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
The species is now known from the following localities: Barbados (A. cmnulata), “in the 
hollows formed in madrepore rocks” (Lesueur) ; Guadeloupe (A. solifera), “in old shells, particularly 
in those of Turbo versicolor" (Lesueur); St. Thomas ( 11. solifera), Duchassaing & Michelotti; Bahamas, 
“attached to the lower surface of the blocks of coral rock, or in cavities in these” (McMurrich); 
Bermudas, “The largest examples were 8 inches or more in diameter when fully expanded, and had 
several hundreds of tentacles. The color is generally light green” (Verrill); Jamaica (Duerden); 
Porto Rico (U. S. Fish Commission). 
The fact that the specimens of this species obtained by McMurrich at the Bahamas are octamerous, 
while the Porto Rican and Jamaican representatives are hexainerous, is of some interest. Eight 
specimens which I have examined all possessed the mesenterial plan represented in lig. 43, and 
McMurrich is quite emphatic as to the arrangement in the forms studied by him. Such variability 
is not unknown in other Actinians. Verrill (1899, p. 216) mentions that he has found specimens 
of Urlidna crassicomis which are hexamerous, both as to tentacles and mesenteries, many others 
decamerous, some octamerous, and a few irregular or unequally developed on opposite sides. 
The freedom of the ventral moieties of the four lateral pairs of mesenteries is a retention in 
the adult polyp of a characteristic met with in larva? and young polyps. In most Actinian and Madrepo- 
rarian young polyps the fifth and sixth bilateral pairs of mesenteries, which correspond with those 
mentioned, remain free from the stomodseum much longer than the other four primary pairs. In most 
instances they continue thus until the pairs of the second-cycle mesenteries are fully established. In 
this connection, also, attention may be drawn to the eight free-swimming larvae, possessed of 24 
mesenteries, described by van Beneden in his beautiful work, “Les Anthozoaires de la Plankton 
Expedition” (1897, pp. 189-194). Although the second cycle of six pairs of mesenteries is fully 
developed in each case, yet in no instance have the fifth and sixth developmental pairs become com- 
plete; only the eight Edwardsian mesenteries extend as far as the stomodfeum. I have reared the 
young polyps of the coral Sideraslrxa radians for a period of seventeen weeks, until the six pairs of 
second-cycle mesenteries were established, and yet the fifth and sixth pairs of primary mesenteries 
remained free from the stomodseum. 
Subfamily METRIDIN.7E Carlgren. 
Sagartidx with column of medium height or low, without papilla?, verruca?, or marginal spherules. 
Sphincter mesogloeal, well developed. Cinclides (chiefly endoderm evaginations) present. Complete 
mesenteries usually six; rarely, especially when only one pair of directive mesenteries is present, more 
than six. Mesenteries of the first order always sterile. Acontia emitted through the cinclides and 
mouth. One or two pairs of directive mesenteries. 
This subfamily includes the four genera, Melridium , Mitactis, Adamsia, and Calliactis. Scarcely 
any differences exist between the last two genera, but they are strongly marked off from the other two. 
Both lladdon and Carlgren state that a cuticle is absent, but in Calliactis tricolor such a formation 
occurs, especially obvious in freshly collected specimens. The scapus is covered with a fairly thick, 
coarse, membranous cuticle, to which foreign particles adhere, and distallv it is often found partly 
detached and hanging loosely. The capitulum is entirely smooth. When polyps are brought into 
the laboratory the cuticle is sloughed off within two or three days, and the. scapus then presents a 
much clearer appearance. 
I have also modified the definition with regard to the extrusion of the acontia. In the West 
Indian Calliactis they are thrown out quite as freely through the mouth as through the cinclides. 
Where, as in Melridium, only one gonidial groove may occur, with only one pair of directives, - 
and the hexameral plan of the mesenteries generally is disturbed, there is every likelihood that the 
polyps are the products of fission. In researches w hich I have recently conducted upon fission in 
coral polyps I find that in the process the stomodieum is usually divided into two equal or nearly equal 
parts, usually at right angles to the directive plane. The mesenteries connected with each half, 
including one pair of directives, go to the formation of a new polyp, or new stomodseal system where 
fission is incomplete. In the new or daughter polyps, however, a new pair of directives appears to 
be never formed, and generally the polyps lose all their hexameral regularity. Hence corals repro- 
ducing by fissiparity are usually devoid of directive mesenteries, except the two primary pairs which 
appear in the larva. No doubt similar relationships hold for Actinian polyps. In the Madreporaria 
gonidial grooves seem never to occur, so that the fate of these structures can not be compared. 
