312 EVENINGS AT THE inCROSCOPE. 



bj means of powerful muscles attaclied to them, a see- 

 saw motion is communicated, which causes the little 

 teeth soon to cut througli the skin and superficial ves- 

 sels, from which the blood begins to flow. The issue 

 of the vital fluid is then promoted by the pressure 

 around, and so goes on until the enormous stomach of 

 the Leech is distended to repletion. 



It has been suggested that this whole contrivance, 

 with the instinct bv which it is accompanied, is in- 

 tended for the benefit of Man, and not of the Leech. 

 Blood seems to be by no means the natural food of the 

 Leech ; it has been ascertained to remain in the stomach 

 for a whole twelvemonth without being digested, vet 

 remaining fluid and sound during the entire period : 

 while, ordinarily, such a substance cannot in one in- 

 stance out of a thousand be swallowed by the animal 

 in a state of nature. "Whether this be so or not — • 

 wdiether man's relief under suffering were the sole ob- 

 ject designed, or not, it was certainly one object ; and 

 we may well be thankful to the mercy of God, who 

 has ordained comfort through so strange an instrumen- 

 tality. 



The progress of marine natural history, as studied 

 in the aquarium, has made our drawing-rooms and 

 halls familiar with a multitude of curious and beautiful 

 creatures which a few years ago were known only, and 

 that very imperfectly, to the learned professors of tech- 

 nical science. Among the forms which embellish our 

 tanks are several species of Serpula, and Worms allied 

 to it. The shelly contorted tube which this painted Sea- 

 worm inhabits, and which it has built up itself around 

 its own body, with stone and cement which that body 

 supjjlied, is well known to you ; as is also the curious 



