PROTOZOA I INFUSORIA. 8 1 



o 



of radiating filamentous tubes, which are furnished at their 

 extremities with suctorial discs, and are capable both of exser 

 tion and retraction. These retractile tubes both seize the prey 

 and serve as vehicles for the ingestion of food ; hence the 

 term " polystome," or many-mouthed, has been proposed for 

 the order by Professor Greene. 



III. ORDER FLAGELLATA. This order comprises those In- 

 fusoria which, like Peridinium, find their means of locomotion 

 in long, flexible, lash-like filaments, termed " flagella ; " cilia 

 occasionally being present as well. In some, as in Peranema 

 (fig. 14, e) t there is only a single one of these appendages ; in 

 others, as in Anisonema, there are two flagella ; whilst in Hetero- 

 mastix and Pleuronema we have forms apparently transitional 

 between the Ciliata and the Flagellata, since both cilia and 

 flagella are present in these genera. In all their other essen- 

 tial characters the flagellate Infusoria do not differ from the 

 more typical members of the class. They have, however, 

 the peculiarity that the base of the flagellum is surrounded 

 by a cup-like or cylindrical membranous collar, which can be 

 retracted at will. In one singular form (Phalansterium intes- 

 tinale), the organism consists of numerous zooids, each with a 

 single flagellum and projecting membranous collar, enveloped 

 basally in slimy sarcode, so as to form a cylindrical colony. 



NOCTILUCA. Amongst the numerous organisms which con- 

 tribute to the phosphorescence of the sea,* one of the com- 

 monest is the animalcule known as Noctiluca, the true position 

 of which has not yet been determined. It is nearly spherical 

 in shape, having an indention, or " hilum," at one side, close 

 to which is fixed a long filament, probably used in locomotion. 

 The body consists of a " cuticle " and " cortical layer," en- 

 closing a central mass of sarcode. Near the filament there is 

 a minute oral aperture leading into a short digestive cavity. 

 A nucleus and vacuoles are also present. From the presence 

 of a mouth, and from its general structure, Noctiluca should 



* The diffused luminosity of the sea is mainly due to the Noctiluca 

 miliaris ; but its partial luminosity is due to various phosphorescent ani- 

 mals, amongst which are the Physalia utriculus (the Portuguese man-of- 

 war), Medttstz, Tunicata, Annelides^ &c. The cause of phosphorescence is 

 variously stated, being supposed very generally to be caused by a process 

 of slow combustion analogous to that which takes place in phosphorus 

 when exposed to the atmosphere. Upon the whole, however, it appears 

 that the phenomenon is a vital process, consisting essentially in the conver- 

 sion of nervous force (or vital energy) into light ; just as the same force 

 can be converted by certain fishes into electricity. This transformation 

 often requires a special apparatus for its production, but it appears to be 

 sometimes effected by the entire organism. 



