AOALEPHyE. 
203 
fictile stems, mutable in form, mouth encircled with a single scries of granulous fill 
forr » tentacula. • . , , „„ , 
h- Seiitiu.aiuam:, plant-like, horny polypiers, rooted and variously branched, tilled 
'l' 41 * semi-fluid organic pulp, the polypes contained within sessile colls disposed along 
sides of the main stem or branchlets, but, nevsr terminal. 
11 1. Medusaiwe. Umbel hemispherical, with marginal tentacula; having eight 
® yea covered by lobes, four ovaries, four cells, four fringed arms, a central opening, 
a,!1 ‘l four lateral openings. 
ti. Siphonophoba, having the animals double, and hell-shaped, one fitting into 
*‘ e Cavity of the other ; in Jhjpliyes the animal has a large air-vessel with numerous 
te “tacula ; in Pkyealia, the animal stretches over a cartilaginous plane. 
ri ‘e true form of the Medusa does not appear in the two first orders. 
Hydraid.e 
Lhe Hydraidae are, according to modern naturalists, Discophoros 
Rested in their development. They comprehend the single genus 
yUra, of which many species are known, whose habits and metamor- 
PWs it will he our object to particularise. 
Hydra vulgaris inhabits stagnant ponds and slowly-running waters. 
1 is of an orange-brown or red colour, the intensity of the colour de- 
eding on the nature of its food, becoming almost blood-red when fed 
^ the small crimson worms and larvae to he found in such places. 
‘ Laurent even succeeded in colouring them blue, red, and white, by 
*“ 6a *8 of indigo, carmine, and chalk, without any real penetration of 
e tissue, the buds from them acquiring the same colour as the mother, 
-Li® the colour of the ova retains its natural tint, eveu when the 
ydi’a mother has been fed with coloured substances during the pro- 
^ ress °f this mode of reproduction. The tentacula, usually seven or 
\Pt in number, never exceed the length of the body, tapering insen - 
S % to a point. 
I[ ydra viridis, the fresh-water polype, being more immediately 
^hin the sphere of our observation, naturally presents itself to our 
otieg ft ig common in ponds and still waters. It was noticed by 
alias, who was of opinion that offspring was produced from every part 
0 tile body. Bo Blahmlle, on the contrary, was of opinion that offspring 
always produced from the same place ; namely, at the junction of 
at part which is hollow and that which is not. Van der Hoven, 
6 Leyden professor, agrees with Pallas, and Dr. Johnston’s opinions 
accoi 'd with Pallas. The green Hydra is common all over Europe, in- 
