PEOTOZOA. 



tenaciously, notwithstanding the growing distension from within, until 

 the force becomes so great that the lips, as they may be called, sud- 

 denly separate, apparently to give vent to some gaseous product. 



(35.) With regard to the reproduction of the species, Mr. Weston 

 assures us that self-division is one mode. First may be noticed a deep 

 depression above and below, not far from the centre of the body ; this, 

 as it increases, throws the tentacles across each other, as a necessary 

 consequence of the depressions in the surface and the position into 

 which the outer membrane (in which the tentacles are inserted) is 

 drawn. As the division proceeds, the two animals steadily, but rather 

 quickly, increase the distance between them, until there is only a long 

 membranous neck, apparently composed first of four, then three, then 

 two irregular lines of cells, which ultimately diminish into a single 

 cord composed of three simple cells, elongated like the links of a chain, 

 and becoming more attenuated till the division is complete. All this 

 latter part of the process is rather rapidly performed ; that is, from the 

 first formation of the rows of cells to the time of the final separation 

 occupies only about a quarter of an hour. 



(36.) The NOCTILUC^: may perhaps be classed with the Rhizopods. 

 The general shape of the Noctiluca* (fig. 6, l) is that of a minute 



Fig. 6. 



melon deeply indented at one extre- 

 mity, at which point is attached a sort 

 of proboscidiform appendage or tail: 

 externally its body seems to consist of 

 two membranes of extreme delicacy, 

 which are apparently filled with a clear 

 fluid. At the bottom of the indenta- 

 tion above-mentioned, close to the 

 insertion of the appendix, there is 

 always found a little mass of mud, or 

 other detritus, which it is very diffi- 

 cult to wash away ; but when this is 

 accomplished, it becomes perceptible 

 that this foreign matter is adherent 

 to a semitransparent granular sub- 

 stance, which here protrudes through 

 a little aperture generally called the 

 mouth, and which is continuous with 

 a quantity of the same material situ- 

 ated in the interior of the little globe. 

 No digestive apparatus is visible; but 

 numerous vacuoles of variable size 

 (fig. 6, 2) are discovered in the gra- 

 nular substance within, together with a central nucleus. No rhizopodic 

 * M. de Quatrefages, Observations sur les Noctiluques, Ann. des Sc. Nat. 1850. 



1. Noctiluca, magnified, and viewed as a 

 transparent object. 2. A portion of its in- 

 ternal tissue magnified 150 diameters, show- 

 ing vacucles and rhizopodic expansions. 



