HIRUDO. 7 
varieties are found in this simple yet wonderful provision of Nature, for 
the perpetuation of living beings,—an egg, through the means of that 
which scarcely occupies definite space in its origin,—of that wherein 
susceptibility of receiving the vital spark may subsist during time incal- 
culable ? 
The capsule consists of a coriaceous, tough, thick imtegument, full 
of tenacious, albuminous, brownish matter. It contains only a single 
embryo, which penetrates the lateral umbo in issuing forth to the light. 
Then the young animal is about an inch in length.—Figs. 12, 15. 
Thus, an aperture in the umbo always denotes its vacancy,—the 
state wherein most of them are recovered from the sea ; for the young 
has generally forsaken its interior. 
The propagation of this species is not strictly confined to any sea- 
son, though belonging chiefly to summer. On opening twenty capsules, 
on September 27, only one contained an embryo. 
A snow-white capsule, very recently produced, was observed in a 
vessel containing a leech, on the 19th of January. Next day, the colour 
had darkened, but the centre of the sole still remained white, nor was 
its ultimate hue attained ina week. A different specimen produced a 
capsule on March 27, another next day, and a third on the 1st of April. 
Thus, the capsules are produced singly, one at a time, though the inter- 
vals may be short. Those of numerous groups, of forty, fifty, or more, 
being in immediate approximation, proceed from a single specimen. 
They form in an extraordinary manner, compared with the external 
capacity. Probably, therefore, they come successively to maturity in 
the ovarium. All may belong to the same animal. On the 10th of 
January, a leech occurred, adhering to the fragment of a shell, bearmg 
seventeen capsules ; an eighteenth was produced on the morning of that 
day week, almost white when noticed ; a nineteenth appeared next day, 
and a twentieth on the 22d of the month. All seemed to be from the 
same parent. 
The greatest number ever seen in a group was fifty-four, of which 
six were in a tier above the others. But all are usually in a single stra- 
tum, wherein the capsules are dispersed irregularly. There is little dis- 
