302 APPENDIX. 



Malacobdella Valenciennsei (page 35). 



I have seen a specimen taken in Mya truncata, from the Firth of 

 Forth, by Dr. P. W. Maclagan ; but, confounding it with the pre- 

 ceding, I made no description. Neither did Blainville discriminate 

 them. He says it is 10-12 lines long by 5-6 in breadth ; and the 

 intestinal canal was much less wavy than it is represented to be by 

 Miiller in M. grossa. 



The following is a translation of Blanchard's description : — "This 

 animal is about 4 centimetres in length, and, at the middle, it is from 

 8 to 10 millimetres in breadth. The colour of the skin is yellowish- 

 white, semitransparent, permitting the intestinal canal to be seen, 

 the colour of which, beyond the oesophagus, is ochre-yellow. The 

 dorsal vessel is distinguished by its whiteness on this coloured in- 

 testine ; and the cerebral ganglions, of a yellowish tint, are also 

 distinguishable through the integuments. The oral aperture is a 

 simple triangular fissure. The anus is round. The sucker is very 

 large, thin, and flattened." 



Pontobdella muricata (page 39). 



" The firm adhesion of the sucker to the skin of its prey must 

 render this animal a cruel and inveterate enemy." — Daly ell. 



This leech has always appeared to us a sluggish animal, lying at 

 the bottom of the containing vessel as if it were half-dead, and con- 

 tracted into an imperfect semicircle*. But Sir J. G. Dalyell, who 

 was remarkably careful of his specimens to keep them in a living 

 condition, found that, although torpid in solitary confinement, it 

 raised itself to activity on the introduction of a companion. " Their 

 necks are intertwined, considerable activity is displayed, and one or 

 more milk-white vesicles, resembling minute grains of oats in figure, 

 are seen protruding from the neck or its vicinity. Some observers 

 have represented a leech, apparently the muricata^ with horns. 

 Have they been deceived by the vesicles ? " 



Pontobdella verrucata (page 40). 



This leech is from 4 to 6 inches in length, and about as thick as a 

 man's little finger. Specimens preserved in spirits are of a cream- 

 yellow colour, with a dusky shade ; but the animal is blackish-green 

 when alive. The suckers are large, thick, and muscular. There 

 are generally six tubercles on the rim of the oral one, but these are 



* "During the day this singular leech reposes in absolute quiescence, but 

 towards evening, its wonted coil relaxes in wider curves, and it rears itself erect 

 on the plane of position, with the head turned inwards. The quiescence of a 

 solitary specimen, however, is interrupted by the introduction of stranger leeches 

 of its own kind ; their society is evidently gratifying. Five having been collected 

 in the same vessel, all began to intertwine their necks together after fixing the 

 sucker ; they stretched and curved, or contracted the body, yet without shifting 

 from their respective spots of adhesion. Such movements continued for hours." 

 — Dalyell. 



