62 A. C. OUDEMANS. 
which in other Hoplonemertea form such a loop. And yet 
the whole head (fifty-seven slices of +> mm. in thickness) was 
very well preserved, judging from certain other peculiarities. 
Between the stomodezeum (which has three distinct layers, an 
inner epithelium layer, a hyaline basal layer, and a circular 
muscular layer) and the muscular layer of the skin (which 
consists here only of the circular muscular layer, outside which 
lie the basal membrane and the skin) we meet in the anterior 
sections (e. g. the tenth) with three layers. Both against the 
circular muscular layer of the stomodeum and against the 
circular muscular layer of the skin we find situated a layer of 
large vesicular cells, with large nuclei, and between these two 
gelatinous stroma occurs. The twolayers of large cells are not of 
one row of cells; the layer against the skin had from two to three, 
the other from four to six rows of cells. The cells are arranged 
more or less radially in both layers. At the common aperture 
we see that the epithelium of the stomodeum passes into that 
of the skin, the hyaline basal layer into the basal membrane of 
the integument, the two circular muscular layers and the two 
layers of large vesicular cells into one another. (The layer of 
gelatinous stroma between the two latter of course ceases in 
front.) The more we go backwards the more in the two layers 
of cells do longitudinal muscular fibres become visible. In the 
layer next to the skin this happens through the whole thickness 
of it, but not in the inner layer. In the inner layer the 
arrangement is thus that we can distinguish an internal layer 
of numerous nuclei (as are figured in figs. 63 and 64. of Langia) 
and an external layer of longitudinal muscular fibres, which 
are arranged in groups. The number of the nuclei just men- 
tioned diminishes on approaching the brain, so that this layer 
close to the brain obtains more the character of gelatinous 
stroma. Gelatinous stroma thus fills the space between the 
two layers of longitudinal muscular fibres, and also the area 
within the inner longitudinal muscular layer, in which area lie 
the central nervous system, proboscidian sheath, intestine, 
vascular system, and generative organs. 
The outer layer of gelatinous stroma is relatively the 
