102 
Z. HYDROIDA. 
Hydra. 
when necessary they can sustain a fast of many weeks without other 
loss than what a paler colour may indicate. Small larvae, worms, 
and entomostracous insects seem to be the favourite food, and to en- 
trap these they expand the tentacula to the utmost and spread them 
in every direction, moving them gently in the water to increase their 
chances, and when a worm, &c. touches any part of them it is im- 
mediately seized, carried to the mouth by these flexible and contrac- 
tile organs, and forced into the stomach. “ ’Tis a fine entertainment/’ 
says Baker, “ to behold the dexterity of a polype in the mastering 
its prey, and observe with what art it evades and overcomes the su- 
perior strength or agility thereof. Many times by way of experi- 
ment, I have put a large worm to the very extremity of a single arm, 
which has instantly fastened on it with its little invisible claspers. 
Then it has afforded me inexpressible pleasure to see the polype 
poising and balancing the worm with no less seeming caution and 
judgment than a skilful angler shows when he perceives a heavy 
fish at the end of a single hair-line, and fears it should break away. 
Contracting the arm that holds it, by very slow degrees, he brings 
it within the reach of his other arms, which eagerly clasping round 
it, and the danger of losing it being over, all the former caution and 
gentleness is laid aside, and it is pulled to the polype’s mouth with a 
surprising violence.”* Sometimes it happens that two polypes will 
seize upon the same worm, when a struggle for the prey ensues, in 
which the strongest gains of course the victory ; or each polype begins 
quietly to swallow his portion, and continues to gulp down his half 
until the mouths of the pair near and come at length into actual con- 
tact. The rest which now ensues appears to prove that they are 
sensible of their untoward position, from which they are frequently 
liberated by the opportune break of the worm, when each obtains his 
share, but should the prey prove too tough, woe ! to the unready ! 
The more resolute dilates the mouth to the requisite extent; and de- 
liberately swallows his opponent, sometimes partially, so as, however, 
to compel the discharge of the bait, while at other times the entire 
polype is engulped ! But a polype is no fitting food to a polype, and 
his capacity of endurance saves him from this living tomb, for after a 
time, when the worm is sucked out of him, the sufferer is disgorged 
with no other loss than his dinner. f This fact is the more remark- 
able when it is contrasted with the fate which awaits the worms on 
which they feed. No sooner are these laid hold upon than they evince 
every symptom of painful suffering, but their violent contortions are 
* Hist, of the Polype, 65. Also Roget’s Bridgw. Treat ii„ 76 
f Trembley, Mem, 112- 
