34 HIRUDO. 



However, in a stratum of ova which appeared on the surface of the 

 belly of two of the smaller leeches in the collection on March 22, and 

 contained apparently in two somewhat circular compartments, I com- 

 puted thirty-three in the larger leech. In both animals a few, seen 

 less distinctly, seemed to be under the stratum. All the ova were quite 

 opaque, not of equal dimensions, but of little sensible difference, and were 

 computed to be about a quarter of a line in length. 



It is thus that the ova appear externally on the body of the parent. 

 Their number, as well as the number into which the whole are divided, 

 is various, according to the individual producing them. On the 29th of 

 March seventy-five appeared in four compartments, the smallest or 

 highest with only eleven. This specimen, fig. 8, was delineated next day. 



The compartments are generally about four in number, as seen with 

 tolerable accuracy ; by superposition there may be more. They are not 

 superficial strata however, but seem upon being dislodged, to be contain- 

 ed in real transparent capsules, each probably invested by its own in- 

 teguments. This displacement may be effected by insinuating the thumb 

 nail suddenly under the sucker. Three capsules, containing twelve, 

 thirteen, and fourteen ova respectively, separated entire, and fell to the 

 bottom of the vessel on March 22. Instead of twenty-four ova, as I had 

 computed in them, there were thirty-nine ; one portion is represented as 

 on March 26 ; fig. 13, enlarged. The parent made no search after them 

 on separation, and affixed itself to a part of the vessel where none lay. 



On the 5th of April nascent leeches were issuing from the proceed- 

 ing capsules ; and the contents of one were entirely dispersed. Therefore 

 those naturalists who affirm that the ovum does not hatch if detached 

 from the parent are mistaken. 



This ovum is of regular conformation, as may be discovered through 

 the thin integument of the capsule. Herein the embryo reposes during 

 the progress of evolution. At an early period it appears as a long obtuse 

 ovoid, then the body is bent, and the head and tail in contact ; and next 

 they recede from each other, and the embryo straightens. The whole 

 embryos are sometimes seen in motion within the capsules, and at length 

 escape from an aperture in the side. They are then pale grey, and 



