TRANSACTIONS OF THE SECTIONS. 131 



On tlie Structure of Noctiluca. B>/ Prof, Allman, F.E.S, 



The author gave an account of some researches he had made on Noctiluca mili- 

 aris. They were mostly confirmatory of the results arrived at by other observers, 

 more especially by Krohn, Quatrefages, Busch, Huxley, and Webb, while they 

 furtlier served to supplement the observations of these zoologists. 



At one end of the meridional depression is the vibratile flagellum with the 

 mouth at its base ; and here the depression becomes quite superficial, while the 

 opposite end is much deeper, and is here abruptly terminated by a vertical wall. 

 Just outside of this deep end of the depression there commences, by a funnel- 

 shaped enlargement, a very slightly elevated ridge of a hrmer consistence thau the 

 rest of the body ; it terminates abruptly after running down, in a meridional direc- 

 tion, over about one third of the eircumfereuce of the body. The author had 

 reason to believe that this ridge is traversed in its length by a canal which opens 

 close to the aboral extremity of the meridional depression by a funnel-shaped 

 orifice. The mouth leads into a short cylindrical gullet ; and the author confirmed 

 the existence of the vibratile ciliuni contained v^dthin the gullet, as originall}' de- 

 scribed by Krohn, and of the ridge, with its projecting tooth, described by Huxley 

 as existing in the gullet-walls. The floor of the gullet is formed by the central 

 mass of protoplasm, here naked and in direct contact with the surrounding medium. 

 The vibratile eilium springs from this floor ; and near the root of the ciliuni is a 

 depression in the floor, which can bo followed for a little distance into the pro- 

 toplasm. 



Besides the well-known branching processes which radiate from the central mass 

 of protoplasm to the walls of the body, there is also sent oft" from the central mass 

 a broad, irregularly quadrangular process, which extends to the outer walls, where 

 it becomes attached along the line of the superficial meridional ridge. The lower 

 free edge of this broad process has the form of a thickened border, and at its upper 

 edge it becomes continuous with a plate-like striated structure, which the author 

 rej^arded as representing a duplicature of the body- walls. 



In contact with the central protoplasm is the nucleus, a clear spherical body 

 about 2^/0 °f ^^ inch, in diameter. 



The "body-walls are composed of two layers — an external thin, transparent, and 

 structureless membrane, and an internal thin granular layer of protoplasm, which 

 lines the structureless membrane throughout its whole extent, and which receives 

 the extremities of the radiating processes from the central mass. Under the action 

 of iodine solution and other reagents, the protoplasmic layer may be seen to detach 

 itself from the outer structureless membrane, and, along with the radiating bands, 

 contract towards the centre. It admits of an obvious comparison with the pri- 

 mordial utricle of the vegetable cell. 



The flagellum, which is given off close to the margin of the mouth, is a flattened 

 band-like organ, gradually nan-owing towards its free extremity, and with its axis 

 transversely striated like a voluntary muscular fibre throughout its whole length. 

 It seems to have the power of elevating its edges, so as to render one of its surfaces 

 concave, and thus becomes converted into a semitube, which may assist in the 

 conveyance of nutriment towards the mouth. 



The nucleus is a spherical vesicle, with clear colourless contents, among which 

 minute transparent o^al corpuscles may usually be detected. When acted on 

 by acetic acid, the difference between tlie contents of the vesicle and its wall be- 

 comes very apparent ; and the contents may now be seen accumulated towards the 

 centre as a minutely granular mass, with some of the oval corpuscles entangled 

 in it. 



The radiating ofl'sets, which extend from the central protoplasm to the peri- 

 pheral layer, contain well-defined clear corpuscles, which slowly change their rela- 

 tive places, as if under the influence of very feeble currents. These oftsets, indeed, 

 closely resemble the radiating protoplasm-filaments which extend from the proto- 

 plasm surrounding the nucleus to the walls of the primordial utricle in the vege- 

 table cell. The peripheral layer contains, scattered through it, numerous minute 

 cell-like bodies : these are spherical and of various sizes ; in the larger ones a 

 fiistinct central nucleus may bo detected. 



