76 CALIFORNIA ACADEIJY OF SCIENCKS. 



Septa. The first very pronounced septum is found between somites iv and v. 

 Beddard 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 setiB of the anterior somites, respectively vii and viii. This makes 

 it appear as if the spermathecre opened in the centre of tlie somite, when in reality 

 they open as usual in the intersegmental groove. 



Alimentary cnnal. 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, (jiz.) 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 oesophagus 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 

 Oligochret.ie. 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 vessel lies almost immediately on the top of the outer or cbloragogic cells, in 

 places penetrating them with connecting vessels which supj^ly the underlining sinus 

 with blood (fig. 47, d. v. c). 



The cbloragogic layer of cells vary considerably in size. Sometimes there is 

 more than one row of cells, one projecting above the other. The nuclei are oval 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 t. 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 lacunes, which in 

 places join the muscular layers (fig. 49 to 53 IL), at other times are more or less 



