KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 51. N:o |l. 7 
cell-strings. The canals and the cell-strings connect the polyps indirectly. The canals 
generally run through the centre of the stolons, except at the base of the polyps, where 
they are situated externally on both sides and communicate with the coelenterons through 
the cell-strings (Fig. 3 and 4). This displacement is the cause of the dilatation of the 
stolons, often seen at the base of the polyps. When the polyps increase in number, the 
stolons and their protuberances coalesce into membranous structures, the arrangement 
of the horizontal canals remaining unchanged. A change may occur, in this case, as, 
owing to the crowding together of the polyps, the connection between them may occur 
directly above the lateral cell-strings (Fig. 4), and the polyps consequently become di- 
Fig. 1. a) Schematic figure of a Cornularia. Fig. 2. Schematic figure of the canals within 
b) Vertical section through the stolon of a a stolon by Clavularia (after HiIcKSON, 1894). 
Cornularia (after v. KocH, 1887). 
rectly connected. This direct connection is, however, secondary, and not of the same 
nature as the primary one in the case of Cornularia. Now there are also species of the 
Clavularia which have a marked membranous development of stolons and few polyps, 
and within these species the horizontal canals are well developed; they do not extend, 
however, direct from polyp to polyp, but, by means of an anastomosis, indirect connec- 
tion between the polyps is maintained. These canals often appear as large, wide cavi- 
ties. 
At a more advanced stage of evolution the growth of the colony proceeds by means 
of an increase in the thickness of the membranous structure, while its horizontal dimen- 
sions tend to decrease. Simultaneously, the coenenchym increases, and a trunk part is 
begun, which, at first, has a low cushion-like form, as in Xena antarctica KUKENTHAL. 
The polyps are inbedded in the coenenchym, and are no longer free 
from each other. At first (as in the case of the family of Xeniidae) it 
is only the basal portions of the polyps which are surrounded by 
coenenchym, but as the colony continues its development, the greater 
become the parts that are surrounded by coenenchym, in addition to 
which the colony becomes higher and, by degrees, ramified. 
This change in the external aspect of the colony corresponds to 
an internal change in the way in which the coelenterons of the polyps Fig. 3. Schematic fi- 
are connected. The stolons, which consist of numerous canals and Sure of a Clavularia. 
a) Section through a 
cell-strings form a tissue, solenia (BOURNE), and this extends in the oto 
coenenchym between the walls of the coelenterons of the close-lying stolon (after v. Koo, 
polyps. The direction of the canals thereby becomes changed; they no Fl 
longer run in an exclusively horizontal direction; they advance along the coelenterons, 
even if not so very distinctively at first, and by means of an anastomosis are connected 
with each other and with the coelenterons — with the latter indirectly. The solenia 
