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Abietinella to Abietinaria and Diphasict. They only differ from 
species of that genus in their hydrothecae being short-stalked, and, 
therefore, a concretion between the stalk and the corresponding 
axis would convert them into Sertularella- species. 
There has not yet been found operculate short-stalked species, 
corresponding to the other genera of the Sertulariidae , but that such 
forms have existed is evident from the faet, that a more or less 
developed stalk-mark is present in most species be- 
longing to this family 1 ) When a branch is regarded from 
one of the sides, this mark as a rule appears as a narrow chitinous 
process forming a continuation of the inner hydrothecal wall and 
riinning either downwards or obliquely inwards, but when we regard 
a hydrotheca from its inner, adeauline wall we see the whole stalk- 
mark (PI. IV, figs. 25, 27) which is provided with a curved or 
sometimes angularly bent proxirnal margin, and, therefore, its middle 
part is mueh shorter than the two lateral margins seeu from the 
sides of the branch. Sometimes, however, we may also be able to 
see the whole stalk-mark, when a branch is regarded from the 
outer surface, f. inst. in Hydrallmania falcata. (PI. V, fig. 7.) 
In some species, f. inst. in Sertularia pumila , Odontotheca trispinosa 
and Abietinaria Coei the stalk-mark when regarded from the 
side has the form of a short coecum-like projection, and in that 
case the stalk must have been provided with an adeauline con- 
cavity, which has prevented it from coalescing with the branch 
in its whole length. In the two former species it is evident already 
from an outer inspection that this projection contains an inner 
cavity (PI. IV, figs. 13, 15, PI, V, figs. 11, 14), the presence of 
which is confirmed by means of a sagittal section through a hy- 
i) While many authors have seen and figured the stalk-mark I have only 
found it mentioned by Clarké (15a) and Ritchie (51). Clarké 
who has seen it in Sertidaria complexa describes it in the following 
way:...: »chitinous processes extend downwards from the base of eacl 
hydrotheca, surrounding an aperture through which the body of th( 
polypite is connected with the cænosarc of the stem.« Ritchii 
who has seen it in Sertularia heterodonta and S. raihbuni mention: 
it in the latter species as »two chitinous processes which projed 
downwards and lie alongside the wall of the internode.« 
