No. 2.] DEVELOPMENT OF MANICINA AREOLATA. 228 
From Fowler’s brief description (15, II.) it would seem that 
the filaments of Wadrepora are essentially like those of Manz- 
cina. The condition of the specimens, however, as the author 
states, did not permit a detailed study. 
The filaments on the secondary are somewhat smaller than 
those on the primary mesenteries. The mesenteric lobes, too, 
are less pronounced, not reaching a development greater than 
is shown in Fig. 54. It has been mentioned that in the upper 
part of their course the secondary filaments become very small. 
Though the diminution in size is so great in this region, that it 
was impossible for me to make out the histological structure, I 
was able to trace the filament as a darkly staining and compact 
mass of tissue into the epithelium of the peristome. The fila- 
ments of the young coral, from which Figs. 41 and 42 were 
made, were like those of the adult, except that the mesenterial 
lobes were less developed. 
I did not study the living filaments, but from the histology it 
is evident that the function of the ventro-lateral tracts is that of 
ciliated bands, while the digestive functions and nettle cells 
are distributed over the three portions of the main body of the 
filament. The mesenteric lobes I regard merely as a device to 
support the filament. 
Before comparing the mesenteric filaments of Mancina with 
the actinian filament as described by the Hertwigs, I will give 
a brief account of the filaments of Cerianthus, this being the 
only actinia I have been able to study by way of comparison. 
In Nassau harbor the larval or free-swimming Cerianthus 
was common. All the individuals I obtained were at about the 
same stage of development. They were oval light brown bodies 
about one-fourth inch long, and had eight or nine very short, 
stubby tentacles. On sectioning the larve, I found they con- 
firmed the theory advanced by the Hertwigs (/c.) as to the 
mode of origin of the mesenteries. Fig. 49 is a section through 
the upper part of the cesophagus. The number of complete mes- 
enteries is fifteen. At one end of the cesophagus is the ventral 
or directive pair of mesenteries, D.JZ, At the other or dorsal 
end are two incomplete mesenteries, 1 and 2, of which the 
former is the younger. The mesentery 3 becomes incomplete 
not far above the cesophageal lip, and 4 follows its example just 
above the lip. From these four mesenteries it may be gathered 
