THE FLAGELLATA. 93 



hasten the process of multiplication by monadiform germs 

 described above. 



Noctiiuca is extremely abundant in the superficial waters 

 of the ocean, and is one of the most usual causes of the phos- 

 phorescence of the sea. The light is given out by the pe- 

 ripheral layer of protoplasm which lines the cuticle. 



The Peridimce {see Fig. 1, /) form another aberrant 

 group of the Flagettata, which lead to the Ciliata. The 

 body is inclosed in a hard case (sometimes produced into 

 rays), which, at one part, presents a groove-like interruption, 

 laying bare the contained protoplasm, in which lies an endo- 

 plast, and in some cases a contractile vacuole. One or more 

 flagelliform cilia, and usually a wreath of short cilia, are pro- 

 truded from the protoplasm, and serve as locomotive organs. 

 The mouth is a depression, whence, in some cases, an oeso- 

 phageal canal is continued and terminates abruptly in the 

 semi-fluid central substance of the body, the food-particles 

 being lodged in vacuoles formed at its extremity, as in the 

 Ciliata. No other mode of multiplication than that by fission 

 has yet been observed in the Perldlnem ; but this fission is 

 sometimes preceded by the inclosure of the animal in an 

 elongated, crescent-shaped cyst. 



(b.) The Testtaculifera. — The Aclnetm (Fig. 9, D, E, 

 F, G) have no oral aperture of the ordinary kind, but filiform 

 processes or tentacula, which are usually slender, simple, and 

 more or less rigid, radiate from the surface cf the body gen- 

 erally, or from one or more regions of that surface. At first 

 sight, these tentacula resemble the radiating pseudopodia of 

 Aetmophrys, but, on closer inspection, they are seen to have 

 a different character. Each, in fact, is a delicate tube, pre- 

 senting a structureless external wall, with a semi-fluid granu- 

 lar axis, and usually ends in a slight enlargement or knob. It 

 may be slowly pushed out or retracted, or diversely bent. 

 But, instead of playing the part of mere prehensile organs, 

 these tentacles act, in addition, as suckers; the Acineta ap- 

 plying one or more of these organs to the body of its prey l — 



1 Stein ("Der Organismus der Infusionsthiere," L, 76) thus describes the 

 method by which an Acineta seizes its prey: "If an Infusorium swims within 

 reach of the Acineta, the nearest tentacles are swiftly thrown toward it, and, at 

 the same time, often become much elongated, bent, or irregularly twisted about. 

 The knob-like ends of these tentacles, which come into immediate contact 

 with the surface of the entano-led prey, spread out into disks, and adhere fixedly 

 to it. When many of the tentacles' have thus attached themselves, the im- 

 prisoned animal is no longer able to escape, its movements become slower, and 

 at length cease. Those tentacles which have fixed themselves most firmly 

 shorten and thicken, and draw the prey nearer to the bodv. . . . Suddenly, as 



