460 University of California Publications in Zoology [Vol.22 



In the pedal region there is a considerable amount of digestive 

 gland, the anterior liver (a. I., pi. 22, fig. 1 ; pi. 23, figs. 6, 7, 8). This 

 communicates with the stomach by several orifices of varying sizes in 

 the right wall (a. st., pi. 22, fig. 1) and by one in the left wall. The 

 latter orifice is in the anterior wall of the lateral pouch (/. p., pi. 23, 

 figs. 6, 7). 



The ventral livers (v. I., pi. 22, fig. 1 ; pi. 23, figs. 6, 7, 8) are small 

 and communicate with the stomach by four small orifices (v. h. o., 

 fig. 1). 



The posterior liver (p. I, pi. 22, figs. 1-4; pi. 23, figs. 7, 8; pi. 24, 

 figs. 10, 11, 12) is a large gland lying on the right side of the stomach 

 at its posterior end. Its large duct opens to the stomach by a very 

 large circular orifice (p. h. o., pi. 22, figs. 1, 3; pi. 24, fig. 11). 

 Deshayes (1845-1848) describes many hepatic orifices in this region 

 instead of the single large one found here in Sigerfoos' (1908) species. 

 Although the posterior liver is externally a unit, it is divided into 

 two parts differing histologically. The cells composing the dorsal 

 part are columnar, making the walls of the acini thick, while the cells 

 of the ventral part are hardly higher than the diameter of their nuclei. 

 This differentiation is indicated diagramatically in plate 22, figures 

 3 and 4, and the external appearance is shown in plate 23, figure 8. 

 The difference in the appearance of the tissues is quite marked in the 

 photomicrograph, plate 24, figure 12. Sigerfoos (1908) describes this 

 same condition in the species he studied. It will be noted that the 

 presumably different secretions of the two parts must mix even before 

 they reach the stomach, which suggests numerous physiological possi- 

 bilities. The anterior and ventral livers exhibit no such differentiation. 



Besides the livers, the stomach bears four other diverticula: the 

 caecum, the sac of the crystalline style, the dorsal caecum, and the 

 lateral pouch. The most conspicuous is the large posterior caecum 

 (c, pi. 22, figs. 1, 5; pi. 23, figs. 6, 7, 8; pi. 24, fig. 13). This equals 

 or exceeds the stomach in capacity. It is cylindrical in shape, but 

 the ventral wall is infolded to form an elaborate, two-coiled typhlosole 

 (c. t.) extending its entire length. This caecum is always found full 

 of wood chips, and it is here, presumably, that wood is digested. Only 

 rarely have evidences of plankton been found in it, though they are 

 common in the intestine. The great capacity of the caecum allows the 

 wood, which is probably slow to digest, to remain there for some time. 

 The typhlosole affords a large area for absorption and has an adequate 

 blood supply. A large artery carries aerated blood directly from the 



