HYDRA. 85 



loured, by the mud usually suspended in sea- water, especially if taken from 

 the flowing tide. Although this be ultimately productive of much embar- 

 rassment to the observer, its presence is so beneficial to various creatures, 

 such as the tunicata, vermes^ annelides, and others, that then they evi- 

 dently thrive, while declining, from its absence, in pure and limpid water. 

 Inadvertence to the fact, I believe, has cost me some valuable specimens. 



Under such circumstances, inevitably supervening as in the preceding 

 tedious course of observations, the watch-glasses should be kept in vessels 

 comparatively of considerable capacity — in those containing perhaps from 

 four to six or eight ounces of water. Also, they should remain in an in- 

 clined position, the convexity outwards, so that the tentacula of the ani- 

 mals pendent within shall have free scope below. Thus the muddy depo- 

 sit, falling on the outside, admits of removal, whereas falling within, the 

 hydrse are liable to injury by attempting it. The observer will find it 

 more difficult to provide against obscurations and interruptions from the 

 insensible residue after feeding the animals, forming a glutinous adhesion 

 to the glass. Then the careful application of a feather, or a hair pencil, 

 will be found useful. 



Sometimes several germinations develope into perfect hydrae, the 

 whole remaining united to the parent. 



A solitary animal having been set apart, it subsequently displayed a 

 family of four well-grown individuals issuing from about the base, to which 

 they still adhered. — Plate XIII. fig. 10. In a week, the evolution of an- 

 other had ensued ; and the formation of two buds, with a serrated margin, 

 besides fig. 11. Original parent in figs. 10, 11, a. 



After undergoing several changes, accompanied by the increase of 

 numbers, this group chanced to be committed to a vessel containing an 

 Actinia, in the confidence of that indemnity to be expected from the quies- 

 cent habits of a kindred race. Yet it was devoured. 



Multiplication advances rapidly under the favourable conditions of 

 genial temperature, copious sustenance, and the element frequently reno- 

 vated. Did they often concur, we should more readily discover colonies 

 of these animals in Scotland. Further elucidations of their history will 

 surprise naturalists at their rarity. 



