302 
POPULAR SCIENCE REVIEW. 
favourite object of attachment to all this group ; here grow, 
but not too closely together, several aquatic plants, — water 
crowfoot, amphibious Persicaria, the copper-coloured Potamo- 
geton (P. perfoliatus ) with transparent leaves like goldbeater’s 
skin, and other plants of the water. 
Now let us go to some sheltered spot or corner of this great 
pool, to which the wind has blown all the floating rubbish, tangled 
masses of Confervse, decayed roots of grasses, feathers of birds, 
etc., and dip our bottles into this heterogeneous mass. Never 
mind the ironical smile of yonder angler, who, proud of the 
pike of twelve pounds weight which he has just succeeded in 
landing about twenty yards from us, accosts himself in 
l’ather a loud tone with “ What, in the name of fortune, can 
that fellow be grubbing after?” No doubt you represent in 
his mind that very eccentric old fellow who, as sung by the 
author of the “ Ingoldsby Legends,” — 
“ Would pore by the hour 
O’er a Aveed or a flower, 
Or the slugs that come crawling out after a shoAver. 
* * * * 
Still poking his nose into this thing or that, 
At a gnat, or a bat, or a cat, or a rat, 
Or great ugly things, 
All legs or Avings, 
With nasty long tails arm’d Avith nasty long stings.” 
You are used to this sort of thing, and continue your dabbling 
in spite of it all. Noav look into your bottle, and you will see 
several small, dark, round bodies, about the size of a pin’s head 
perhaps ; take three or four out, and examine them singly on your 
hand with your lens. “ They are slightly convex on one side, 
and concave on the other.” “ Then they are of no use except as 
indicators ; they are merely the separated discs or faces of old 
specimens ; try again.” “Noav what have you?” “Why, amass 
an inch long, and of an oval shape.” “These agglomerated masses 
are to be depended on, so we Avill take them home, and in due 
time you will see them germinate.” These httle bodies are the 
product of the most beautiful of all the Fresh-water Polyzoa, 
and of one which is generally considered to be somewhat rare, 
viz., Cristatellcu Mucedo, the only locomotive species ; for, 
unlike the rest of the family, Gristatella is unattached, and 
being possessed of a muscular base, strongly resembling the 
foot of a gasteropodous mollusc, the colony is enabled to move 
about, slowly, it is true, upon the surface of submerged weeds, 
stones, etc. But it is extremely difficult to detect the presence 
of adult forms of Gristatella, on account of them transparency, 
and the fact that they live for the most part upon weeds which 
