NOCTILUCA MILIARIS. 11 



its axis shows through its entire length transverse striae. It seems to 

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

 surfaces concave, and thus to form a tube-like process. This 

 flagellum must not be confounded with the whip-Uke tentacle 

 to which I have already referred, though there are some points of 

 resemblance between the two : their position and difference in 

 size form the great distinction. 



As many, however, as fifty individuals may sometimes be 

 examined without discovering this minute organ. The tail-like 

 tentacle may be easily seen with a pocket-lens, whilst a quarter- 

 inch objective will be required to discern the cilium, or flagellum. 

 Springing from the base of this tail-like appendage to the edge of 

 the oral aperture is a ridge-like prominence, something in the 

 shape of the letter S, apparently of a horny nature, and crowning 

 this ridge is a tooth-like process, with three cusps, or divisions of 

 unequal character. This tooth is one seven thousandth part of 

 an inch high. Professor Huxley states that he has seen no move- 

 ment in this organ ; but another writer, Dr. Webb, throws some 

 light on the subject by stating that he has seen the ridge contract, 

 and that he has observed a backward and forward movement of 

 the tooth as though working on an axis. It is easily broken, and 

 becomes shrivelled up by the use of astringents. 



With regard to an excretory aperture, sound observers have 

 come to the conclusion that egesta are voided from the mouth, but 

 the opinion of the few writers that we have upon this subject 

 appears to be much divided. Just below this mouth-Uke aperture, 

 or tube, there is a depression corresponding in shape, as I have 

 said before, with an ordinary peach, and the base of this depres- 

 sion, which is funnel-shaped, appears to have some communica- 

 tion with one of the gastric pouches. Krohn states that he saw 

 excrementa voided from the groove of the body, but he is unable 

 to define the exact point. Huxley, though he has no precise data 

 to go upon, thinks that from the general structure of the organism, 

 a distinct anus must exist, and that the funnel-shaped communica- 

 tion must, therefore, serve that purpose. 



From the rapid apparent change of shape which the Noctiluca 

 presents whilst swimming about, and its continual alteration of 

 position, it is by no means easy to get a clear and uninterrupted 



