NOCTILUCA. 



197 



of the sea, and possesses a peach shaped body which is surrounded by 

 a cuticular envelope, and bears a tentacle-like appendage. A furrow- 

 like invagination is situate at the base of this appendage, at one 

 end of which is the mouth close to a tooth-like prominence and a 

 slender vibratile nagellum. The soft body consists of a central mass 

 of contractile protoplasm, connected by fine and anastomosing threads 

 with a layer of the same substance which lines the cuticular envelope 

 of the body. In the central protoplasm lies a clear body, the nucleus; 

 and the spaces between the radiating processes, which exhibit the 

 phenomena of granule currents, are filled with fluid. The contractile 

 substance extends into the appendage, and there assumes a cross- 

 striped appearance (fig. 136). 



N 



FIG. 136. A'orftfKea miUaris (partly after Cienkowski). N, Nu- 

 cleus, a, Single animal, b, conjugation of two individuals, 

 c and d, swarm spores. 



The reproduction takes place by means of fission (Bright well), pre- 

 ceded by division of the nucleus ; or by spore formation (Zoospores). 

 In the latter case, the nagellum is absorbed or thrown off, and the 

 Noctiluca assumes a spheroidal shape. After the disappearance of 

 the nucleus, the sarcode contents accumulate on the inner side of 

 one region of the cuticle, divide into from two to four masses which 

 are not sharply separated from one another, and the cuticular envelope 

 is thrust out into a corresponding number of protuberances. These 

 buds increase and form numerous wart-like prominences, the future 

 spores. They arise, therefore, at the expense of the protoplasmic 

 contents of the disc, which is gradually exhausted in their for- 



