i 
SERTULAIIIA CUSCUTA OF ELLIS. 489 
may induce a belief that they are merely parts of that sys^ 
tern, and destined by the currents which they produce, to 
bring the small animals, their prey, more easily within 
reach of seizure. The currents, however, which are pro- 
duced by their motion, seem better calculated for bringing 
fresh portions of water in contact with the sides of the 
arms, than to bring animalculae within the space which 
they surround. They may possibly be destined to act as 
organs of touch, though I am rather disposed to regard 
them as branchitSy placed in the most favourable position 
for receiving the influence of the oxygen of the water. 
In that part of the body of the expanded polypus, situate 
towards the middle and bottom of the cell, I observed a 
pale-coloured organ with darker matter both above and 
below. This organ was frequently in very rapid motion, 
by means of which portions of the dark matter beneath 
were brought up and added to that which was above the 
organ, or portions abstracted from above and carried be- 
neath. The portions of matter moved were not unlike 
grains of sand, which had probably been taken in along 
with the food. 
The small egg-shaped bodies in some parts of the 
branches, which were regarded as vesicles or ovaria by 
Ellis, are merely the rudiments of young polypi. It is 
probable, however, that, after having served the purposes 
of polypi, they may be changed into ovaria. This is a 
metamorphosis which takes place in some of the other kinds 
of Sertulariae, and is not more surprising than the conver- 
sion of the cell and its polypus into a branch, as I have 
elsewhere observed. We are apt to consider these animals 
as simple in their construction, possessing few organs, and 
exercising very limited functions ; and, when they are confe- 
pared with the Vertebral tribes, the opinion is perhaps 
well founded. But we may carry this view too far, and. 
