76 MANUAL OF ZOOLOGY. 



of ladiating 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, Hke 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. lo, (?), there is only a single one of these appendages ; in 

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

 mastix And Pleuronema -wthsye forms apparently transitional 

 between the Ciliata and the Flagellata, since both cilia an'd 

 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. In one singular form 

 {Phalansterium intestinale), 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 cylin- 

 drical 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, Nodiluca should pro- 

 bably be looked upon as a flagellate Infusorian, but it is placed 

 by M. de Quatrefages amongst the Rhizopoda. 



* Thj 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), 

 Medusa, Tunicata, Annelides, Sec. 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 phosphonis when ex- 

 posed to the atmosphere. Upon the whole, however, it appears that the 

 phenomenon is a vital process, consisting essentially in the conversion 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 some- 

 ^times effected by the entire organism. 



