90 ZOOPHYTES. 



others had dropped from their site. Many are thus lost with the lapse of 

 time, and some are also dislodged accidentally. In about two years, or 

 little more, from the commencement of observation, when the number was 

 ten only, the whole consisted of about sixty hydrse remaining, and now 

 dispersed over both surfaces. In two years and a half, however, those 

 adhering to the shell were reduced to nine, disposed on the sides towards 

 the lower edge. 



Gradual decay and deperdition still impaired their number, for the 

 shell became very brittle with age, and it is this, amidst other inconve- 

 niencies, that aggravates the embarrassment of watching the progress of 

 subjects. 



After repeating several incidental observations, previously made on 

 mutilated organs, I considered it necessary to ascertain more decisively 

 the kindred nature of this hydra of the sea to the fresh-water species of 

 Scotland, so as to warrant its incorporation or otherwise with the same 

 genus. 



I do not recollect that naturalists have ascribed the property of re- 

 covering lost organs to any but perfect animals : for, if I be not mistaken, 

 the numerous experiments related of regenerated parts, were made on 

 those in their ultimate stage. 



Nevertheless I confess myself extremely averse to such experiments, 

 though no such tender scruples are entertained by others. Besides, where 

 practicable, it is better that our studies should be confined to animated 

 beings unconstrained and uninjured. 



About the middle of October, or six weeks after new treatment had 

 improved the group on the razor shell, the specimen, PL XIV. fig. 1, a, 

 was bisected. In a fortnight, a row of regenerating tentacula extended 

 two lines from the stump or under portion ; and in another week the 

 mutilated animal had become entire. It was delineated on February 13, 

 or four months from the date of the experiment, along with its com- 

 panions, all in the cavity of the shell, being seen at that time as above 

 quoted, — somewhat exceeding nature — a, fig. 1, PI. XIV. There it 

 remained unchanged, but much enlarged, eleven or twelve months after 

 bisection 



