ON PTYCnODERA FLAVA. 183 



EXPLANATION OF PLATE 5, 



lUustratiug Mr. Arthur Willey's paper "On Ptychodera 



flava, Eschscholtz." 



Fig. 1.— Dorsal view of Ptychodera flava. The annulations of the 

 genital pleura are indicated anteriorly on the left side ; those of the body 

 proper behind the hepatic region, pr. Proboscis, c. Collar region, b 

 Branchial region ; the genital pleura are slightly divaricated, and the pharynx 

 is visible, p.b. Post-branchial region, h. Hepatic region, l.s. Dorso 

 lateral streaks marking the course of the ciliated grooves in the intestinal 

 wall. d.n. Line marking the course of the dorsal nerve-cord. a. Anus. 

 Drawn from the living object. 



Fig. 2. — Anterior portion of another individual from the dorsal side, show 

 ing the tuberosity caused by a Copepod parasite. The cross-lines over the 

 infested region represent continuations of the annulations of the genita 

 pleuron. 



Fig. 3.— Portion of the pharyngeal wall of P. flava, including the lower 

 portions of three tongue-bars, to show the larger size of the latter as com- 

 pared with the primary bars. The lower free extremities of the tongue-bars 

 are differentiated from the rest of the bar, being marked off in each case by a 

 pigmented line of demarcation, t. b. Tongue-bars. p. b. Primary or septal 

 bars. SI/. Synapticula. g. s. Gill-clefts, ce. s. (Esophageal ridge (= 

 Grenzwulst of Spengel), forming the boundary between the branchial and 

 oesophageal portions of the alimentary canal. Drawn from a preparation in 

 formol. Zeiss cam. Inc., oc. 3, obj. A. 



Fig. 4. — Groups of male gonads of P. flava sketched from a detached 

 piece of the genital pleura. 



Fig. 4«. — A single testis from the branchial region with the pigment 

 patches over its surface. 



Fig. 5. — Groups of female gonads of P. flava with ova. The portions of 

 the gonads not occupied by the ova are filled up with coarse mucous (?) 

 granules. 



Fig. 6. — An artificially liberated ovum of P. flava surrounded by the 

 double-contoured follicular membrane. Zeiss cam. luc, oc. 3, obj. D. 



