NOCTILUCA 769 



their light, which is of a beautiful greenish tint, and is vivid enough 

 to be perceptible by ordinary lamp-light. This luminosity is but of 

 an instant's duration, and a short rest is required for its renewal. A 

 brilliant but short-lived display of luminosity, to be followed by its 

 total cessation, may be produced by electric or chemical stimulation. 

 Professor Allman found the addition of a drop of alcohol to the water 

 containing specimens of Xoctiluca. on the stage of the microscope, 

 produced a luminosity strong enough to be visible under a half-inch 

 objective, lasting with full intensity for >everal seconds, and then 

 gradually disappearing, lie was thus able to satisfy himself that 

 the special seat of the phosphorescence is the peripheral protoplasmic 

 reticulation which lines the external structureless membrane. 



The reproduction in this interesting type is effected in various 

 ways. According to Cienkowskv. even a small portion of the proto- 

 plasm of a mutilated Xoct'dnca will (as among rhizopods) reproduce 

 the entire animal. Multiplication by fission or binary subdivision, 

 beginning in the enlargement, constriction, and separation of the two 

 halves of the nucleus, has been frequently observed. Another form 

 of non-sexual reproduction, which seems parallel to the 'swarming 

 of many protophytes, commences by a kind of encysting proce->. 

 The tentacle and flagellum disappear, and the mouth gradually 

 narrows, and at last closes up ; the meridional groove also disappears, 

 so that the animal becomes a closed hollow >phere. The nucleus 

 elongates, and becomes transversely constricted, and its two halves 

 separate, each remaining connected with a portion of the protoplasmic 

 network. This duplicative subdivision is repeated over and over 

 again, until as many as 512 genimules ' are formed, each consisting 

 of a nuclear particle enveloped by a protoplasmic laver. and each 

 having its flagellum. The entire aggregate forms a disc-like mass 

 projecting from the surface of the sphere ; and this mass sometimes 

 detaches itself as a whole, subsequently breaking up into individuals ; 

 whilst, more commonly, the genimules detach themselves one bv one, 

 the separation beginning at the margin of the disc, and proceeding 

 towards its centre. The genimules are at first closed monadiform 

 spheres, each having a nucleus, contractile vesicle, and flagellum ; 

 the mouth is subsequently formed, and the tentacle and permanent 

 flagellum afterwards make their appearance. A process of 'conjuga- 

 tion' has also been observed, alike in ordinary Xoctilacw and in their 

 closed or encysted forms, which seems to be sexual in its nature. 

 Two individuals, applying their oral surfaces to each other, adhere 

 closely together, and their nuclei become connected by a bridge of 

 protoplasmic substance. The tentacles are tin-own off, the two bodies 

 gradually coalesce, and the two nuclei fuse into one. The whole 

 process occupies about five or six hours, but its results have not been 

 followed out. 1 



1 Noctili/ca has been the subject of numerous memoirs, of which the following 

 are the most recent: Cienkowsky, Arch f. micros. Anat. Bel. vn. 1871, p. 181, and 

 Bel. ix. 1873, p. 47; Allman, Quart. Juu.ru. Microsc. Sci. n.s. vol. xii. 1872, p. 327 ; 

 Robin, Journ. de I'Anat.et de Phijsiol. torn. xiv. 1878, p. .586; Vigiial, Arch. ,lr 

 Phi/sioL set. ii. torn. v. 1878, p. 415; Stein, Der Organismus dcr Iiifusionsthiere, 

 iii.2, 1883; and Biitschli, Morplwl. JaJirbuch.x. 1885, p. 529. For the group of 

 which it and the Mediterranean genus Leptodiscits (Hertwig ) are the representatives, 

 Haeckel has suggested the name CystaflugrUata. 



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