346 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
forms of Campanulariidae having a free, branched, primary stem are 
classed under the genus Laomedia s. ext. with three subgenera, 
Obelia, Gonothyraea, and Laomedia s. str ., including in the latter 
all of those branching forms which have hitherto been placed in the 
genus Campanuiaria. Finally, the latter genus is characterized by 
a simple, unbranched primary stem and by a thick diaphragm which 
consists of two parts, one “thick and rather high, a ring-formed 
process from the beaker ; the other a thin chitinous membrane which 
is secreted from-the basal part of the hydranth.” In genera, on the 
other hand, which are characterized by a free, branched, primary 
stem “ the diaphragm shows no such distinction in outer and inner 
parts” (Marktanner-Turneretscher, ’95, p. 400). 
The application of this latter differential in placing species leads 
only to “ confusion worse confounded.” Levinsen and Marktanner- 
Turneretscher use Campanuiaria integra as a type showing the 
double diaphragm in which the lower layer is extremely thick. 
This is undoubtedly true here, and a thin “ membranous ” layer is 
found above it, as shown in fig. 12 f, PI. 6, but in the closely allied 
C. caliculata we find the extremely thick portion, with no trace 
whatsoever of the thin membranous partition (PI. 6, fig. lln). 
Again in the free branching forms, according to these observers, the 
diaphragm “ shows no distinction between inner and outer parts.” 
Campanuiaria gracilis is a branching form with free and erect stem 
(PI. 3, fig. 13), but the diaphragm has two distinct layers, an upper 
and a lower (PI. 6, fig. 13d); and Obelia dichotoma , another 
branching and erect form has a distinctly double diaphragm. What 
now becomes of the differential? 
Schneider has severely criticised the use of the diaphragm as a 
differential character and comes to the unequivocal conclusion that 
“ die Diaphragmabeschaffenheit hat fur die Systematik der Genera 
gar keine Bedeutung ” (’97, p. 512). 
Thus the question stands, and we are no nearer well-defined diag¬ 
nostic characters than heretofore. The diaphragm, however, may 
be more important than Schneider is inclined to believe, for in the 
Puget Sound species there are well-defined differences and all grada¬ 
tions in the different genera and species.. In C. caliculata the 
thickened portion at the base of the polyp is not a part of the stalk 
but an inner thickening of the hydrotheca, and to all intents and 
purposes is a diaphragm (PI. 6, fig. 11d). In no case is the dia¬ 
phragm anything but an ingrowth of the chitinous periderm, but 
