76 CALIFORNIA ACADEMY OF SCIENCES. 
Septa. The first very pronounced septum is found between somites iv and y. 
3eddard has already remarked that the septa in Pontodrilus hesperidum are unusu- 
ally thickened, some of them being thicker even than the body-wall at the point 
where they are attached to it. The septa in our present form are almost gradually 
increasing in thickness towards the one between xi and xii, which septum is the 
thickest, being almost as thick as the ventral body-wall. The septum dividing xii 
and xiii, while thickened, is much thinner, and those bounding the somites down to 
xix are almost normal in thickness, that is, equal those posterior to the clitellum. As 
a rule the attachments of the septa correspond with the intersegmental furrows. The 
septa bounding vii/viii and viii/ix are, however, exceptions as far as the place of their 
ventral attachment is concerned. These two septa are here affixed to the body-wall 
half-way between the sete of the anterior somites, respectively viiand viii. This makes 
it appear as if the spermathece opened in the centre of the somite, when in reality 
they open as usual in the intersegmental groove. 
Alimentary canal. The alimentary canal takes the shape of a long, narrow 
duct, singularly straight and without any prominent characteristics until it reaches 
somite xiv, in which somite commences a kind of gizzard of peculiar construction 
(fig. 29, giz.) Though this organ resembles a gizzard in outward form it is in reality 
no gizzard at all, but rather a glandular modification of the alimentary wall. With 
a gizzard we must of course mean an enlargement of the alimentary canal in which 
the muscular part has reached an enormous development in order to grind the food 
properly. In the organ referred to in our present species the muscular layers are on 
the contrary not increased in size, the thickening of the wall being caused exclusively 
by a new layer composed of glandular cells, which has been interposed between the 
transverse muscles and the inner epithelium, thus forming a glandular crop between 
the cesophagus and the tubular intestine. This organ occupies three somites, Xiv, xv, 
xvi, or very much the same place as is so frequently the location for gizzard in other 
Oligochete. If we view a longitudinal section of the body through this crop (fig. 47) 
we find it to be more or less tapering towards either end. The large longitudinal 
blood yessel lies almost immediately on the top of the outer or chloragogic cells, in 
places penetrating them with connecting vessels which supply the underlining sinus 
with blood (fig. 47, d. v. ¢.). 
The chloragogic layer of cells vary considerably in size. Sometimes there is 
more than one row of cells, one projecting above the other. The nuclei are oyal and 
situated at the place where the cells become narrower. The longitudinal muscular 
layer is narrow, about two strands thick, immediately superposed the transverse layer, 
which consists only of one single thickness of strands (fig. 48 to 54 ¢. m.) The case gen- 
erally observed in gizzards is that this layer is composed of a great number of strands 
more or less regularly arranged around a central plate. Below this transverse layer, 
commences the very thick layer of glandular cells, about 12 cells wide in centre. 
In the upper part of this layer are seen numerous blood laeunes, which in 
ro 
places join the muscular layers (fig. 49 to 53 0/.), at other times are more or less 
