4 McMURRICH. (VoL. III. 
ACTINIARIA. 
Tribe Hexactini#, Hertwig. 
Actiniaria, with paired mesenteries, those of each pair pro- 
vided with longitudinal muscle fibres on the faces turned towards 
each other, and transverse fibres on the faces turned away from 
each other, — except in the case of two pairs, the directives, in 
which the arrangement is reversed, the longitudinal muscle 
fibres being upon the outer surfaces, and the transverse fibres 
on the inner. The number of the pairs of mesenteries present 
is at least six, and they increase in multiples of six, 
Sub-tribe ACTININZE 
= Family Actinine, Andres. 
Hexactiniz, with simple uniform tentacles, situated towards 
the periphery of the disc, so as to leave the central portion bare ; 
each tentacle corresponds to an intraseptal space, and they are 
arranged in cycles, and not in radial series. 
Family Sagartide, Hert. 
Actininz, adhering to foreign bodies by a flat, contractile 
base. Column smooth, or provided with verrucz or tubercles, 
and perforated by cinclides. Sphincter muscle usually well 
developed and imbedded in the mesoglcea,! occasionally absent 
or very feebly developed (Aiptasia). The mesenteries of the 
first cycle alone are perfect, and are not gonophoric, the repro- 
ductive organs being borne by the mesenteries of the second 
and third cycles. The free edges of all the septa with mesen- 
terial filaments bear acontia. The tentacles are smooth, cylin- 
drical, entacmzeous, and are arranged in regular cycles. 
The definition of the family Sagartidz given above is essen- 
tially identical with that of R. Hertwig (82), the only difference 
1 Being convinced that the supporting layer of the Actiniaria cannot be con- 
sidered homologous with the mesoderm of the higher forms, I have adopted for its 
designation the term mesoglocea proposed by Bourne (Quart. Fourn. Micr. Sci.,N.S., 
Vol. XXVII., 1887). 
