354 THE SPONGIDA OR PORIFERA. 



for example, in collared monads from Syca7idra coiiipressa 

 (Fig. 3 a^ Plate XVI.), and Sycandra ciliata (Fig. 2, Plate XV.). 

 Saville Kent describes the collar (Fig. 5 a, Plate XVI.) as an 

 organ of great importance, which can only be satisfactorily studied 

 by means of the highest objectives and strongest illuminating 

 apparatus, at the same time that the animalcule is supplied with 

 artificial coloured food, such as powdered indigo or carmine. 

 Under such conditions, " it will be found that the collar consists 

 of a transparent infundibuliform film of sarcode, that may be 

 protruded from and withdrawn at will into the general substance 

 of the monad's body, in the same manner as the sarcode prolon- 

 gations or pseudopodia of an Amoeba or other Rhizopod. As in 

 the pseudopodia of certain Rhizopods, such as the Foraminifera, 

 it will moreover be found that, notwithstanding the extreme 

 tenuity of the sarcode films, a circulation of its substance is being 

 constantly maintained ; flowing upward on the outside, over the 

 distant edge, and downwards on the inner surface, at the base of 

 which it again comes in contact and merges wdth the protoplasmic 

 substance of the body. The wine-glass-like film of sarcode 

 doubtless acts as an efficient branchial or respiratory organ, but 

 such by no means represents its most important function. In 

 conjunction w^ith the centrally-enclosed flagellum it constitutes a 

 most admirably contrived trap, or snare, for the capture and 

 retention of the animalcule's food. Whirling round with incon- 

 ceivable rapidity, the last-named organ, the flagellum, creates a 

 strong centrifugal current in the water, setting in from behind 

 towards the direction of its own apex, and bringing with it all 

 such tiny organic particles as do not possess sufiicient weight or 

 power to stem its tide. But for the outstretched collar, these 

 would simply hurry with the stream past the monad's body, and 

 out of reach. Not for them, however, so easy a passing of the 

 rapids ! In the midst of their swift career they strike against the 

 almost impassable films of sarcode of which the organ is com- 

 posed, and to this they adhere as tenaciously as a snared bird to 

 a lime-daubed twig, or an incautious fly to a spider's web. Then 

 slowdy, almost imperceptibly, the captive atoms are carried along 

 with the circulating current of the collar's substance up the out- 

 side, and down the inside, until, on reaching the base of its inner 



