ON ARHYNCHUS HEMIGNATHI. 209 
distance into the genital pore. Beneath this is the true epi- 
dermis, or subcuticle as itis called; this has in my specimens 
the usual structure met with in the group so well described by 
Hamann, and consists of a matrix of a fibrillar nature, the 
fibrils being as a rule arranged radially, in which are embedded 
a certain number of ameeboid nuclei (figs. vi and x). This tissue 
is much thicker in the region of the collar than elsewhere, and 
it is thicker in the trunk than in the head. It is pierced in all 
directions by a series of tubes or lacunze which have no definite 
lining, but which seem to be mere splits in the fibrillar matrix. 
The lacune—except in the head—have a general circular direc- 
tion which is very well marked in the trunk region where each 
runs into a lateral longitudinal split (fig. x). They contain a 
small amount of coagulum, the remnant of the fluid which 
circulates in them ; during life this fluid, in other species, holds 
in suspension fat and coloured oil globules. If these are 
present in my species they must have been dissolved out in 
the processes which precede embedding. The circular lacunze 
of the trunk not only communicate with one another by means 
of the two longitudinal lateral lacunee (fig. xiv), but they open 
into one another by numerous small branches which have an 
oblique or longitudinal direction. In the head the lacunz 
have a general longitudinal course; they are not, however, 
straight, but twist in and out between the pits on the surface ; 
they anastomose freely (fig. iv). Thus in a transverse section 
of the head the lacunze appear as round holes more or less uni- 
formly arranged in the skin, and the same effect is produced 
by a longitudinal section of the trunk. 
In the collar region the subcuticular tissue is much thick- 
ened, and the lacunar system forms a single more or less 
definite ring which gives off numerous branching anastomosing 
twigs (fig. v). 
Although the above account attempts to give the general 
course of the lacunz in the skin, it should be mentioned 
that there is considerable irregularity in the arrangement, 
and one is almost inclined to believe that the canals do not 
remain permanent, but that they sometimes close up and 
VoL. 39, PART 2.—NEW SER. O 
