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 Allmaii found the addition of a drop of alcohol to the water 

 containing specimens of Noctiluca, on the stage of the microscope, 

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

 objective, lasting with full intensity for several seconds, and then 

 gradually disappearing. He 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 Cienkowsky, even a small portion of the proto- 

 plasm of a mutilated Noctlluca will (as among rhizopods) reproduce 

 the entire animal. Multiplication by fission or binary subdivision, 

 beginning in the enlargement, const riction, 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 process. 

 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 sphere. 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 

 jigaiii, until as many as 512 'gemmules' are formed, each consisting 

 of a nuclear particle enveloped by a protoplasmic layer, 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 gemmules detach themselves one by one, 

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

 towards its centre. The gemmules 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 Noctilucce 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 thrown 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 Noctiluca has been the subject of numerous memoirs, of which the following 

 are the most recent : Cienkowsky, Arch f. micros. Anat. Bd. vii. 1871, p. 131, and 

 Bd. ix. 1873, p. 47; Allman, Quart. Journ. Microsc. Sci. n.s. vol. xii. 1872, p. 327; 

 Eobin, Jo urn. de I' Anat. et de Physiol. torn. xiv. 1878, p. 586; Vignal, Arch, de 

 Physiol. ser. ii. torn. v. 1878, p. 415; Stein, Der Organismus der Infusionsthiere, 

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

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

 Haeckel has suggested the name Cystoflagellata. 



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