MOEPHOLOGY OF CYCLOPS. 23 



(PI. III. fig. A), narrow slips, most of them inserted into the junction of the labruni 

 and epistonia; but the uppermost pair cross the internal divaricators of the lower 

 limb of the gullet to be inserted into the upper end of the anterior edge of the 

 epistome. 



The posterior apertors of the mouth, are one or two paired slips, from the lower 

 surface of the entosternite, the chief work being done here by the retractors of the 

 postoral bar. 



The gullet (PL III. fig. 4, ce.) is a short tube bent at a sharp angle halfway up, so 

 that it is divided into a lower limb running upwards and forwards, and an upper limb 

 running upwards and backwards. The lining membrane of the gullet is strongly 

 chitinized, longitudinally plicate when contracted. It is certainly in parts fringed with 

 very fine (gustatory ?) setae. Its constrictors are complete hoops of muscle. 



The anterior divaricators of the lower limb (PL III. fig. 4) are paired slips, originating 

 in the ventral and anterior edge of the epistoma, and inserted by brush-like ends 

 abutting against the cuticle ; the posterior divaricators have similar relations at their 

 insertion into the posterior wall of this limb and converge to their origin on the lower 

 side of the anterior edge of the entosternite. 



The divaricators of the angle of the gullet (PL III. fig. 4) are a radiating series 

 of paired muscles inserted between the base of the rostrum and the socket of the 

 antennule ; between the sockets of the antennules and of the antennae, those of the 

 antenna? and of the mandihles, those of the mandibles and the maxillae, each muscle 

 consisting of at least two slips ; a strong pair to the angles of the free entosternite ; 

 and a posterior pair, crossing the posterior divaricators of the lower limb to be inserted 

 behind them on the lower surface of the entosternite in front of the attachments of the 

 retractors of the postoral bar. The two most anterior pairs of these divaricators perforate 

 the brain. 



The upper limb (PL III. fig. 4) of the gullet is surrounded by about six complete 

 constrictors, in two groups, an upper and a lower, of three each. The anterior dicuri- 

 cators (or better, perhaps, levators) of this limb arise from the carapace just behind 

 and below the insertion of the anterior (shorter) muscles of the antennule, and diverge 

 to their insertion ; a strong bundle is inserted between the two groups of constrictors, 

 and two others in the intervals between the three upper constrictors. There are no 

 posterior divaricators to this limb. 



Stomach (PL III. figs. 1, 5). — This is an oval sac, extending back to about the second 

 thoracic segment, the gullet opening by a transverse slit into the lower part of its 

 anterior end. Its anterior third differs from the rest in being lined by a thin chitiuous 

 cuticle (" intima" of Leydig), secreted by a flattened hypoderm, and thrown into longi- 

 tudinal folds wdien contracted. The muscular coat of this part is composed of very fine 

 irregularly arranged muscles, contrasting strongly with their regular disposition over the 

 rest of the stomach. This part of the stomach may be compared with the chitinized 

 gizzard found in all Crustacea except the Phyllopods and some of the Copepods them- 

 selves. The rest of the stomach is lined by large vacuolated columnar cells, loose at 

 their rounded ends, which project into the cavity of the stomach ; their ovoid nucleus lies 

 near the base of the cells. They contain fat-globules in the anterior part, and posteriorly 



