THE MAST1GOPHORA 



189 



The nucleus is lodged within the central protoplasm, and 

 presents during life a transparent, homogeneous appearance. 



The ingested food is enclosed in food-vacuoles, Avhich are some- 

 times so large as to occupy the greater portion of the body. No 

 contractile vacuole has been observed. The products of metabolism 

 consist of albuminoid and fatty granules. 



Neither the slow contractions of the tentacle nor the rapid 

 vibrations of the cilium are sufficient to impart movements of pro- 

 gression to the inert body of Noctiluca, which merely drifts with the 

 rest of the plankton, kept afloat by its own buoyancy. The 



FIG. 13. 



Sporulation by blastogenesis in Noctiluca miliaris, Sur. A, surface view of the germinal 

 disc, showing the nuclei that give rise to the nuclei of the spores. Each nucleus (n) is accom- 

 panied by an archoplasmic body (a). B, cleavage-products (buds) in side view. C, L>, buds 

 in process of division. The archoplasmic body () is seen to have divided before the nucleus 

 (/(). K and F, later stages of blastogenesis. (After Doflein.) 



phosphorescence of Noctiluca is the manifestation of its response to- 

 mechanical, electrical, thermal, and chemical stimuli. According 

 to the observations of Quatrefages (quoted by Watase), " the light 

 emitted from the whole body, or any of its parts, is composed of a, 

 vast number of instantaneous scintillations." 



The life-history of Noctiluca comprises the phenomena of simple 

 longitudinal fission (Fig. 15), resting-phase, conjugation, and blasto- 

 genesis. The transition of an ordinary individual into the resting 

 condition does not involve the formation of a protective cyst- 

 membrane, but simply the degeneration of the peristome and its 

 annexes. 



When two individuals come together for the purpose of con- 



