on the Hirudo vulgaris. 
21 
EXPLANATION OF THE DRAWING. 
Fig. i . A front view of the Hirudo vulgaris , of its natural 
size. 
Fig. 2. A back view of the same. 
Fig. 3 The appearance it presents previous to its deposit- 
ing the capsule. 
Fig. 4. The eyes (magnified) showing their arrangement. 
Fig. 5. A portion of the abdominal blood-vessel, magnified, 
showing its diamond-figured dilatations. 
Fig. 6. The globular form of the capsule, when unattached, 
(of its natural size).— a, its appearance at the moment of de- 
position : b , the appearance it afterwards assumes. 
Fig. 7. The form of this membrane (also of its natural 
size) when attached to any surrounding body. 
Fig. 8. The capsule, magnified, showing the included ova, 
{a a) the points from which the young escape. 
Fig. 9. The appearance of the ova at the end of a fort- 
night. 
Fig. 10. The ova at the expiration of the third week, when 
animal existence is first observed. 
Fig. 11. The appearance of the young at the termination 
of the sixth week, when they are about to quit the capsule. 
JAMES RAWLINS JOHNSON. 
Bristol, October 30, 1816. 
