164 



HARDWICKE'S SCIENCE-GOSSIP. 



[July 1, 1867. 



MXCKOSCOPY. 



Examining Soundings, etc. — As I was looking 

 through a great many specimens of foraminiferous 

 soundings from the Indian ocean, which I received 

 through the kindness of Mr. Latimer Clark, I felt 

 much inconvenienced by constantly stretching my 

 neck towards the sky in order to examine the objects 

 in a good light with my Coddington lens. More- 

 over, it took some time and trouble to fix some of 

 the ooze between the two plates of glass. A glass 

 prism happened to lie on the table, and I found that 

 if the object is laid on one side of the same, and 



Fig. 172. Section of Prism. 

 indicates the position of the object. 



which is held horizontally, then the other side will 

 reflect the sky light through the object into the eye 

 in a manner exceedingly pleasant to the observer. 

 In this manner a drop of water may be examined, 

 which will not run off. A rectangular prism I found 

 to be better suited then an equilateral one, and it 

 may be mentioned that the quality of glass beiug of 

 no consequence, the expense of one is very trifling 

 indeed. I mentioned this application of the prism 

 to several microscopic friends who did not know of 

 it, and I think its publication in the Science- 

 Gossip may be a welcome hint to microscopists. — 

 C. Becker. 



Movement of Diatoms. — Mr. Bockett's idea of 

 the nature of the motive power of diatoms is very 

 ingenious ; but, as it differs from the opinion I 

 have formed after a long course of observation, I 

 venture to offer a few notes upon the subject. We 

 may take it for granted that a diatom moves by 

 means of organs, acting either upon the water 

 surrounding it, or upon the solid matter over which 

 it glides. That it moves with considerable force is 

 evident from the ease with which it pushes its way 

 through particles of sand, and masses of tangled 

 conferva. To produce this force, any organs acting 

 only upon the water would have to move with con- 

 siderable velocity, and would cause a commotion in 

 the immediate neighbourhood of the diatom, which 

 would be rendered plainly visible by the agitation 

 of the minute particles floating in the water ; but 

 no such disturbance is perceptible. Besides this, 

 the diatom would have the power of moving when 

 suspended in the water, but it appears quite helpless 

 when so situated. We may therefore reasonably 

 conclude that diatoms do not move by means of 

 organs acting upon the water. Of the other known 

 modes of propulsion, there are only two which seem 

 worthy of consideration ; the first of these, by 



means of the protrusion of sarcode or eudochrome, 

 so as to form pseudopoda, seems unlikely, from the 

 consideration that if such organs existed 1 , we might 

 reasonably expect that they would be visible in our 

 microscopes ; the steady uniform gliding motion of 

 the Naviculse seems rather to point to the other 

 form of motive power, the type of which we find in 

 the Gasteropoda; that is to say, in wave -like 

 motions of the so-called foot. It is generally ad- 

 mitted that diatoms have an external layer of soft 

 homogeneous matter, which has to be removed with 

 acids in the process of preparing the valves for 

 mounting. It is possibly in this layer, and in the 

 line of the keel, that the power of motion is situated. 

 I have observed that the Navicula3 always move 

 with their keel pressed against the substance over 

 which they are passing; I have seen them leave 

 the glass slide, and pass over a surface perpen- 

 dicular to it, and in doing so they have turned over 

 at right angles so as to keep their keel pressed 

 against the new surface ; even iu this position I 

 have seen nothing of the wave-like motion, but it is 

 quite possible that it may never be seen, for even in 

 a snail it is only visible under exceptional condi- 

 tions, such as when it is seen crawling over a pane 

 of glass. I have fancied that I have seen a motion 

 of this nature in Bacillarice, and it is difficult to 

 account for the movements of those singular 

 organisms in any other manner, as all who have 

 watched their wonderful military-like manoeuvres 

 will admit. We see what we may call a company 

 slowly stretch itself out into a long single file, then 

 in an instant, as if anticipating a charge from some 

 of the lanceolata about, fall back and form square 

 " with inconceivable rapidity." Now if we suppose 

 that each member of this company has the power 

 of gliding along its neighbour, it is evident that 

 acting simultaneously, no more time will be required 

 for the whole line to draw back than for one of the 

 diatoms to crawl its own length. — F. IF. .1/". 



What to do, and now to do it.— He who 

 would learn the exquisite delights Nature has for 

 those who ardently pursue her, and would acquire a 

 deep sense of reverence and piety in presence of 

 the great and unfathomable mysteries which encom- 

 pass life, must give his mornings to laborious 

 searchings on the rocks, his afternoons to patient 

 labour with the microscope. — Lewes' "Sea-side 

 Studies." 



Medium Size. — The largest animal known is the 

 llorqual, which is about 100 feet in length. The 

 smallest is the Twilight Monad, whose dimensions 

 are 12,000th of an inch. It is evident that the 

 middle term is £rd of an inch, about the length of 

 the common house fly, which may therefore be con- 

 sidered as an animal of medium size in the creation. 

 —P. E. Gosse. 



