APPENDIX. 315 



In many specimens the interranea are very obvious from the pel- 

 lucidity of the body. They form a pinnated leaf down the back, 

 the lateral cseca, which are six in number, curving neatly and regu- 

 larly backwards, and the two posterior continued backwards in a 

 straight line. 



In G. marginata there is a single egg in each capsule. 



Mueller says that, when at rest, this leech is about equal in breadth 

 at both ends, which the specimens in spirits would seem to confirm. 

 The colour of the back, when in life, is greenish, with many brown 

 lines ; but, in spirits, it is ochre-yellow, with pale brown lines, on 

 which the whitish prominent tubercles are placed. These are in six 

 rows, nearly equidistant, one on each side of the mesial line, two 

 lateral rows of lesser granules, and two almost marginal. The margin 

 is neatly crenulate or regularly waved. The ventral surface is paler 

 than the dorsal, and unicolorous in spirits. The head is continuous 

 with the body, and it is very difficult to detect any appearance of 

 eyes. 



From G. cojnplanata it differs in its greater size, and in being less 

 narrowed in front ; in colour ; in the number and form of the dorsal 

 granules ; and in the proportion of the intestinal appendages. It is 

 also more active. 



Glossiphonia sexoculata (page 51). 



"The natural abode of this species is in lakes or ponds, on the 

 under surface of stones, on decaying wood, or in the recesses formed 

 by the folds of the Iris and other aquatic plants." — Balyell. 



This species does not leave the water, but it will often raise its 

 anterior part beyond the surface, and remain thus for several days. 

 Even when entirely submerged, I have known it remain stationary 

 for a long time. Hunger does not stimulate it to move but at long 

 intervals. Miiller says that it can live a quarter of a year at least 

 without food having been ever perceptible in the intestine. It " feeds 

 abundantly on both animal and vegetable substances ; " it preys espe- 

 cially on shelled mollusca, and is a cruel foe, against which the snail 

 can find no defence, either in its shell, or in its tenacity of life. 

 When alarmed, the leech coils itself up into a ball — the hedgehog 

 of the pond, and protects the head by the broader posterior end. 



G. sexoculata is oviparous. "The chief season of breeding is 

 March and April, and it continues throughout summer. Many are 

 very prolific." There are from six to twelve ova extruded at a time, 

 not in a capsule, but "held together by some gelatinous matter* ; " 

 and about fifty ova in all are produced at a birth. These are 

 received into the abdominal pouch of the parent, where they remain 

 until they are hatched, which is in about twelve or fourteen days. 

 The young continue attached to this marsupium for some time, fixed 

 by the anal sucker, and waving the body at will ; but they frequently 



* But Grube says that there are from five to seven ova enveloped in a very 

 transparent soft saccular egg-case.— /?«/?. Ray Soc. Zool. 1847, p. 513. 



