58 



SCIENCE-GOSSIP. 



different foci may be (relatively) greatly magnified, 

 and as the eye-pieces are so arranged that the 

 lower focal point in every eye-piece lies in the same 

 plane when they are in their places in the tube, no 

 change of focus is involved, although we secure 

 true and accurate increase of magnification. 



Thus, if we use say a 240 mm. objective — what 

 we have so long called a one-inch power — its 

 initial magnification will be 105. No. 1 compen- 

 sation eye-piece will give that only without 

 magnification. But the eye-pieces are arranged in 

 series, and are marked with the number of times 

 they magnify this initial magnification. Thus, if 

 we use an initial magnification of 105 and an eye- 

 piece numbered 4, it brings the magnificaticn to 

 forty-two diams. 



Now we can, with quite satisfactory results, 

 magnify by the eye-piece an inital power of 105 in 

 the objective to 280 diams., and as this leaves the 

 focus unaffected for practical purposes, it gives us 

 a means of research on certain objects which we 

 had not within our reach before. 



For many \ears the habits and activities cf 

 Mcliccrta ringens have afforded me the keenest 

 pleasure and interest, and to many of these I have 

 applied with admirable results the advantageous 

 properties of the apochrcmatic system ; and there 

 is one point in which it has yielded an interesting 

 result. 



In the summers of 1893 and 1S94, 1 was fortunate 

 enough to come upon an exceedingly abundant 

 supply of these organisms, and they were net only 

 very plentiful but extremely vigorous ; moreover, 

 many of them were evidently cf greater age than 

 those I had usually seen. This was manifest in 

 the great comparative length of some of their 

 tubes, and the remarkably graduated sizes the 

 pellets presented from the base to the top edge ; 

 also in the confluence or " weathering " of these in 

 the lower and middle rings, and in the numerous 

 growths of algae, diatoms, conferva, and other 

 things upon the tubes. 



An average one drawn from life is shown in fig. 1. 

 The intense and rapid action of the cilia arrested 

 even an eye familiar with the object ; and the lobes 

 assumed a great variety of soft and beautiful 

 curves, not unusual but never so frequently seen 

 before. A very common one of these is shewn in 

 the illustration. 



It is not too much to assume that the readers of 

 this journal are familiar with all the actions of this 

 beautiful rotifer as a brick-maker and a tube 

 builder. It is familiar to all that by the cilia about 

 the edge and upon the bosom of her petal-like lobes 

 r.he obtains a vertical stream of particles which are 

 with wonderful delicacy separated into material 

 serving for food and material serving for the 

 manufacture of the pellets, which are afterwards 

 used as " bricks " to build her tube in a succession 



of rings. We may perhaps be pardoned none the 

 less for borrowing a figure from Dr. Hudson (fig. 2) 

 which shows the cilicated lobes, the "chin" (ch), 

 the pellet in its mold or cup (pm), and the 

 antennas (an). 



Mr. P. H. Gosse says: "Below the larger 

 petals (that is, on the ventral side) there is a 

 projecting angular chin (ch, fig. 2) which is 

 ciliated ; and immediately below this is the little 

 cup-like organ .... a small hemispherical 



cavity On my mixing carmine with 



the water the course of the ciliary current was 

 readily traced, and formed a fine spectacle. The 

 particles are hurled round the margin of the 

 disc until they pass off in front through a great 



sinus between the larger petals If the 



atoms be few, we see them swiftly glide along the 

 facial surface, following the irregularities of outline 

 with beautiful precision, dash round the projecting 

 chin (ch, fig. 2) like a fleet of boats doubling a 

 bold headland, and lodge themselves one after 

 another in the little cup-shaped receptacle beneath 



(pm, fig. 2) The contents of the cup 



are whirled round with great rapidity " ( 5 ), and 

 become the bricks or pellets with which the tube 

 is built. 



Now the fact that these pellets or " bricks " were 

 deposited in rings, constituting the familiar tube, is 

 a mere common-place of the natural history of 

 minute life. In his first and most original paper, 

 Mr. Gosse, having seen the brick produced, says : 

 " I now watched the animal with eager expecta- 

 tion, and presently had the satisfaction of seeing it 

 bend forward its head, as I had expected, and after 

 a second or two raise it again, when I saw that the 



little cup had lost its contents This 



process I saw repeated many times in succession, 

 until a goodly array of pellets were laid .... 

 but very irregularly ' : ( c ). 



Again, in regard to a young melicertan, "A 

 pellet was quickly formed and instantly deposited 

 at the foot ; the same operation w r as repeated with 

 energy and industry, so that in a few minutes a row 

 of pellets were seen forming a portion of a circle 

 around its foot-base " ( 7 ). 



Again, the pellet having been formed, " Suddenly 

 now we see the animal bend itself forward, till the 

 cup is brought into contact with the upper edge of 

 the case, it remains so bent for an instant, and then 

 as quickly resumes its upright position. The cup, 

 however, is now empty ; for the consolidated pellet .... 

 has been left on the edge of the case " ( 8 ). 



In the same way that most careful and acute 

 observer, Judge Bedwell, tells us in regard to the 

 deposit of the " brick," that "It does it so quickly, 

 that before you have got over the agitation and 

 surprise which its unexpected and rapid change 

 of position causes you, the act, like a conjuring- 

 trick, is over, and the anfmal is in its old position 



