IQ2I.] 



Fauna of the Chilka Lake : Leeches. 



669 



note applicable to this leech, with numerous minute spots of faint pink on the dorsal 

 surface. 



The eyes are entirely absent. No trace of visual organs could be detected even 

 in sections. 



The epidermis consists of a layer of cells 

 covered with a cuticle. Among the epidermic 

 cells are, as is usual, glandular cells for the sec- 

 retion of mucus. Immediately beneath the epi- 

 dermis lies the dermal musculature which is 

 strongly developed, consisting of two sets of 

 fibres, outer circular and inner longitudinal. The 

 circular muscles form a continuous sheet of great 

 thickness, while the longitudinal muscles occur 

 in distinct and thick bundles. Widely scattered 

 in the parenchyma are numerous glands, which 

 represent a large and round cell as is seen in P. 

 caeca. 



The mouth is placed in the centre of the 

 anterior sucker, leading into the usual pharyn- 

 geal sheath, which extends backwards into about 

 somite IX. Within the sheath lies the pharynx, 

 which commences as a short slender and cylin- 

 drical tube just behind the brain. Opening into 

 the posterior end are a pair of groups of the 

 salivary glands, each group consisting of a bunch 

 of numerous large gland- cells. The long oesop- 

 hagus leads into the crop, which is produced 

 laterally into five pairs of irregularly outbulged 

 pouches in somites XV-XIX, the last of which 

 connects with the stomach, without being pro- 

 longed posteriorly into a blind sac. The stomach 

 is provided with four pairs of simple pouches, 

 coming off somewhat metamerically in somites 

 XX-XXIII. The intestine follows, and passes 

 to the dorsally situated anus between somites 

 XXVI and XXVII. 



The vascular system agrees in the main with 

 that of Pontobdella and some others, the dorsal 

 vessel being situated outside the dorsal sinus, but coming inside it occasionally. 

 It becomes dilated in the anterior and middle regions of the body into a spaci- 

 ous sac to surround the pharynx and oesophagus with its coeca. In the region 

 of the pharynx the dorsal coeca send out on each side lateral branches, communi- 

 cating with the ventral vessel, where the latter forms a complete loop. In some sec- 



— an. 



Fig, 4. — Diagrammatic representation 

 of the organization of Pterobdella'amara, 

 as seen from the dorsal side. Index let- 

 ters as in fig. 1. 



