450 Happon— The Actiniaria of Torres Straits. 
The mesenteries of the specimen examined consist of two pairs of directives, 
and four pairs of perfect mesenteries on one side, and six on the other; in 
each exoccel, there is one central pair of moderately developed, imperfect 
mesenteries, on each side of which is a pair of much smaller ones; the total 
number of mesenteries being 48 (124+ 124 24); but a sexradiate symmetry 
is not maintained. 
The retractor muscle of the mesenteries is on the whole very feeble; but 
towards its distal end (¢.e. near the mesenterial filament) it forms a small pro- 
turberance (PI. xx1x., fig. 5). The parieto-basilar muscle is very feeble, only a few 
small plaits could be discerned on the side of the mesentery bearing the retractor 
muscle. 
There were no gonads in the specimen that was sectionised. 
An irregularity in the number of the perfect mesenteries is characteristic of 
the genus Sagartia. 
Dr. Carlgren (1893, pp. 98, 99) finds in the typical variety of Sagartia undata 
(O. F. Miill.) that a hexamerous arrangement of the mesenteries is by no means 
adhered to, and also, as occurs in other species of Sagartia, only one pair of direc- 
tive mesenteries may be present, instead of the normal two pairs; the first, second, 
and even the third cycles of mesenteries may be perfect. In one specimen, with 
one pair of directives, Carlgren found the formula for the pairs of mesenteries as 
follows 5 + 5 +104 20 + 40, and in another 8 + 8 + 16. Other irregularities 
were observed. In one specimen, with mesenteries arranged in a symmetry of 8, 
there were no directives present, and the animal was completely radial. Two 
examples were met with having three directives, in another (var. wndata B) were 
eleven perfect and eleven imperfect pairs of mesenteries. The arrangement of 
the mesenteries in one specimen was as follows (D.5.D.3.D.8) + 14 4+ 28, 
and in another(D.5.D.6)+ 18 + 26; that is, in the former there were 
three directives separated, respectively, by five, three, and three pairs of 
mesenteries all of which were perfect, the remaining cycles were imperfect; 
and in the latter thirteen pairs of mesenteries were perfect, including the 
two directives. One young specimen of var. wndata a, had precisely the con- 
dition which occurs in the adult Gonactinia (cf. Trans. R. D. S. 1v., 1889, 
pp. 3841, 354). 
Still more recently, M*Murrich (Zool. Bulletin, Boston, 1., 1897, p. 117) 
describes the following irregularities in seven specimens of Sagartia spongicola, 
Verr. Two are arranged on the hexamerous plan, two on a heptamerous plan, 
and three on an octamerous; in one specimen there are two pairs of directives 
(which are not opposite each other), in five there are three pairs, and in one 
specimen four pairs of directives. 
