FLAGELLATED INFUSORIANS 



3539 



PHOSPHORESCENT ANIMAL- 

 CULE, Noctiluca. 

 (Magnified 150 diameters.) 



On calm dark nights during the summer and autumn the surface of the sea is 

 occasionally seen to be pervaded by a beautiful bluish or greenish luminosity. 

 The appearance of the phosphorescence is somewhat capri- 

 cious, but it will best be seen on calm warm nights when 

 there has been a gentle sea breeze for several days. This 

 strange phenomenon has attracted attention from the 

 earliest times, but it was not till the middle of the eighteenth 

 century that the cause was discovered. The luminosity 

 is in most cases due to the presence of multitudes of tiny 

 jelly spheres, each smaller than a pin's head. On taking 

 up a tumbler of the sea water, the spheres frequently form 

 a thick layer at the surface. By separating a few of the 

 organisms on blotting paper, the light emitted will enable 

 one to see the time by a watch, at a distance of a foot or more. A few organisms 

 swimming or floating about in plenty of sea room in a tumbler of water, will not 



become luminous unless the water be shaken 



about, but when crowded together, they become 



diffusely luminous, owing to mutual jostling and 



irritation. The luminosity in an individual sphere, 



which should be inspected with a lens, may appear 



as a sudden, generally 



diffused flash, followed 



by darkness or by less 



intense light, or again, 



in the form of brilliant 



points of light. The 



name of the organism, 



which belongs to the 



flagellated infusorians, is 



Noctiluca. The body 



forms a peach-shaped cyst, about one-fiftieth of an inch in 

 diameter, and with a tough membranous wall. A groove 

 on the surface sinks at one end into a funnel leading into 

 the interior. From the interior of the funnel there arises a 

 large transversely striated flagellum, or proboscis, by means 

 of which the animal swims, and there is also in the 

 same place a fine whip-like flagellum. At the apex of 

 the funnel there is a mass of sarcode, which extends 

 itself as a wide-meshed, highly-vacuolated network, to 

 the inner wall of the cyst, where it forms a thin layer, 

 whence the phosphorescence emanates. Noctiluca 

 multiplies by dividing into two, or by becoming encysted, 

 after drawing in its flagella, and breaking up into numer- 

 ous ciliated helmet-shaped ' ' swarm pores. ' ' Fre- 

 quently two organisms fuse into one which may then 



(Magnified 100 diameters.) 

 Pyrocystis. 



MUSSEL ANIMALCULE (Sty- 

 lonychia mytilus) UN- 

 DER SURFACE. 

 a. Mouth ; b. Contractile vacu- 

 ole ; c. Nucleus. 



(Magnified 150 diameters.) 



