273 



ordinary conditions, the movement is most active, Avhile 

 during the afternoon it is very shiggish, and at night ahnost 

 nil. This Amphora, as I saw it at the time mentioned, Avas 

 moving even more rapidly than I ever saw a^aci/Zanamove, 

 and that with a steady onAvard progression very different from 

 that of most naviculiform diatoms. 



It appears to me that in Schizonema and similar genera, 

 which consist of siliceous loricated naviculiform frustules 

 enclosed in membranous tubes, as soon as a rupture of the 

 investing membrane takes place, by fracture or tearing 

 asunder, almost immediately a knowledge of the fact is in 

 Some way communicated from the point at which the open- 

 ing occurs to all other points of the tube, as at once the 

 contained frustules Avhicli hitherto have been at perfect 

 rest or, at most, only moving to a very slight extent, and 

 even then in an extremely sluggish manner^ become ani- 

 mated in their motion, and the most of them move towards, 

 and attempt to escape from, the opening made. And this 

 evidently does not result, as might at first have been sup- 

 posed, from any pressure exerted upon them from the closed 

 end of the tube, and Avhich, therefore, only shows itself when 

 the obstacle in the shape of the investing membrane is sud- 

 denly removed. For the motion is the true lively action 

 peculiar to the living individual in the naviculiform Dia- 

 tomacese, and is not in all cases towards the opening made, 

 but often many, or, as in some cases which have come under 

 my observation, most of the frustules begin to move in an 

 opposite direction at first, Avhile at the same time many escape 

 by the opening in the tube, and thereafter assume vigorous 

 motion in the surrounding liquid. Again, usually some of 

 the frustules being, as at first appears, carried along by the 

 stream constituting the mass of those moving towards the 

 opening, all of a sudden seem to change their minds, or are 

 struck with an idea^ if I may so exjiress myself, and here and 

 there will be seen individuals which at once alter the direc- 

 tion of their course and move in exactly the opposite directiou, 

 or backwards, as Ave may say. The individual frustules as 

 they escape from the ruptured end of the investing tube and 

 enter the surrounding Avater, do so Avith the peculiar trem- 

 bling and apparently uncertain movement so characteristic of 

 many of these organisms. 



It Avill be well to note that these observations have been 

 mainly made on Schizonema Grevillei, a species occurrin^T 

 very commonly in Ncav York harbour, although I have 

 noticed the same thing to happen Avith other species of the 



VOL. X. NEW SKR. T 



