HYDRA. 75 



side, like the bud of a vegetable ; and while the offspring was yet adher- 

 ing to the parent, to witness another — a second race of descendants — 

 originating from the first generation, seemed a disturbance of the ap- 

 pointed order regulating the conditions of existence. But, above all, to 

 find a being endowed with life and sensation, as if indestructible under the 

 edge of the knife, so that privation of the most important parts of the 

 frame for conducting the vital functions, was only a prelude for the de- 

 velopement of others to supply their place, revived the fabulous hydra of 

 the ancients in actual verification. 



Thus was the notice of physiologists irresistibly attracted to those 

 energetic qualities of living matter restoring organic integrity. 



Extending the field of inquiry, they proposed to apply to other 

 creatures of the lower tribes, the name of the animal, the hydra, by which 

 such admirable peculiarities had been displayed. Herein their plan was 

 partly correct, and partly erroneous ; for, taking only a superficial view of 

 the aspect of such animals, those anatomical distinctions sanctioning their 

 transference to other genera, either remained undiscovered, or they had 

 not sufficient weight to lead to their removal. 



Hence it is, perhaps, that hydra is rather a conventional term of 

 general application than a rigid definition employed to signify that peculiar 

 structure of the animal exclusively falling under it. 



The only Scotish Hydrae of the fresh waters, which I can positively 

 identify as different, are thefmca and viridis of the Linnean Systema ; the 

 former with six or seven tentacula, the latter with six, eight, or more. 

 But the number of each is indefinite. — PI. XII. figs. 14-20, inclusive, 

 enlarged, 



I do not recollect to have found the first with above seven tentacula. 

 The young are pullulating from the sides of all but figs. 14-17. Fig. 15 was 

 white or pale grey, which may be an accidental variety. 



Neither of these species, especially the green, is uncommon in Scot- 

 land ; but the properties and peculiarities of the genus having been long 

 ago so copiously exposed by Trembley, Bonnet, Roesel, Baker, and other 

 skilful experimentalists, it would be superfluous to discuss their history 

 here. 



