PROTOZOA: INFUSORIA. IOI 



and to which much of the phosphoresence of the sea is due.* 

 It is of large size and spherical in form, with an indentation or 

 " hilum " at one side, where the mouth is situated, and beside 



Fig. 34. Suctorial and Flagellate Infusoria. A, Podophrya; B, Cercomonas truncata ; 

 C, Monas neg lecta ', D, Eiigleua sanguinea ; E, Ccdosiga pulcherrima ; F, Astasia 

 trlchophora ', G, Heteromastix proteiforwis. _/" Flagellum ; in Collar at the base of 

 the flagellum ; c Contractile vesicle ; n Nucleus ; e Eye-spot. (After Pritchard, 

 Ehrenberg, and James-Clark.) 



which is fixed a single long flagellum. The body consists of 

 a central vacuolated mass of protoplasm, surrounded by a 

 superficial layer, and in turn invested by a thin cuticle. The 

 superficial layer is connected with the central protoplasmic 

 parenchyma by numerous radiating, branched, and anastomos- 

 ing filaments of sarcode. The luminosity appears to reside in 

 nucleated cellular bodies in the outer layer of the central pro- 

 toplasm that is to say, in the peripheral layer of sarcode im- 

 mediately below the cuticle. 



* 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), Medusa, Tunicata, Annelides, &c. The cause of phosphorescence is 

 variously stated, it being supposed very generally to be the result of a pro- 

 cess 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 

 appears generally to require a special apparatus for its production. 



