OF POLYPES. 
45 
they still continue the rapid vibration of their cilia ; and though 
severed from the polypus, the tentacula continue to move for- 
ward through the water; the severed tentaculum of a flustra is 
seen to swim through the water like a worm. The number of 
those organs varies much ; they are eight in Serialaria lendigera, 
and in Plumularia falcata, fourteen in Cellaria avicularia, twenty- 
two in Flustra carbasea. The effect of those motions of the 
cilia again is obviously to change the stratum of water constant- 
ly in contact with the most delicate fleshy parts of those zoo- 
phytes, with the highly organized soft irritable fleshy polypi. Thus 
they aerate the cellular texture of their body, at the same time 
that they bring the animalcules — their ordinary food — within the 
grasp of the tentacula.”* 
All polypes — ascidian and hydraform — subsist on animal mat- 
ter, feeding upon it either in a living state, or dissolved and sus- 
pended in the circumfluent medium. The Hydrse and smaller 
species seize on worms and animalcules brought accidentally with- 
in reach, or carried into the vortex formed by the play of the 
tentacular cilia :f the larger kinds (Helianthoida) swallow small 
crabs and shelled mollusca, rejecting the shells after having 
sucked out the soft contents. The food, in the Hydroida, is 
dissolved and necessarily made chylous in the stomach, and di- 
rectly absorbed from it ; but in the ascidian it is probable that 
the process of chylification is not completed until the food has 
passed into the intestine. In the higher animals the chyle is 
mixed with the blood and exposed to the influence of atmosphe- 
rical air before it is fitted for assimilation and growth ; and though 
bloodless, this air is no less necessary to the growth and exist- 
ence of polypes, which soon languish and die in vessels of un- 
* Lect. Comp. Anat. in the Lancet, 1834, Vol. ii. p. 959 “ All the cilia ap- 
pear to commence and to cease their motions at the same moment. The con- 
stancy with which they continue would seem to exclude the possibility of their 
being the result of volition ; and they are, therefore, more probably determined 
by some unknown physical cause, dependent, however, on the life of the animal.’’ 
Roget, Bridgew. Treat, i. 173. 
f “ II seroit cependant possible de croire que ces animaux pourroient aussi 
bien se nourrir d’animalcules que les Hydres ; mais Cavolini dit positivement 
que, quoiqu’il ait souvent observe des polypes de gorgones, de millepores dans 
des eaux remplies d’animalcules, il ne les a jamais vus essayer a en saisir avec 
leur tentacules.” Blainville, Man. d’Actinol. p. 97. Raspail nevertheless proves 
that they feed on them. — Mem. Soc. Hisb Nat. iv. p. 88. 
