SCIEXCE-GOSSIP. 



brighter portion of the rings has slightly increased 

 in width since the latter part of last centur\-. 



Again, it is very hard to believe that the inner 

 dark ring, usually known as the " crape veil," has 

 not become far brighter during the present 

 centurj-. In iS8o the writer could not possibly 

 have overlooked it with a 4j-in. silver-on-glass 

 Newtonian. But early in the century Sir J. 

 Herschel and Schroeter were studj-ing the planet 

 v,-ith mirrors more than four times that aperture, and 

 overlooked it altogether. That it was in existence 

 is v,-ell known, for in 1715 the j-ounger Cassina saw 

 it where it crossed the planet. But it was not until 

 1S33 that Dr. Galle, of Berlin, saw something of it, 

 and not until the autumn of 1S50 that Bond and 

 Tuttle, in America, and W. R. Dawes, in England, 

 discovered its true character. These things added 

 to the laws of motion seem to definitely point out 

 the fact that the rings, so far from being solid, are 

 really composed of a multitude of little bodies 

 travelling around the planet. Long ago the 

 yoimger Cassini suggested something of this sort, 

 and now in later times Professor J. Clark ^Maxwell 

 and R. A. Proctor have advocated the same 

 explanation. 



The spectroscope is a marvellous instrument for 

 answering difficult questions, and in 1S05 Professor 

 Keeler, of the .\lleghany Observatory-, applied it to 

 the study of the rings of Saturn, It has long been 

 known that if a star were approaching the obser%"er 

 the dark lines in its spectrum were displaced 

 towards the \iolet, whilst if the source of light 

 were receding the displacement was towards the 

 red. More than that, the amount of the displace- 

 ment varied according to the rate of such motion. 

 The application of this method of research to the 

 rings of Saturn shows that the inner portion of 

 the ring of the eastern or follovving ansa at 

 its broadest part is travelling towards us at a 

 certain rate, the outer portion of the ring is also 

 approaching us at a certain rate. In the opposite 

 ansa the motion is of course from the observer. 

 Were the bright rings a solid plane the motion of 

 the outer edge would exceed that of the inner 

 almost as 5 : 3, so that if the slit of the spectroscope 

 were laid along the equatorial diameter of the 

 planet and rings, the inner edge on the / side would 

 displace the lines towards the \iolet, and the dis- 

 placement would be increased to the outer edge. 

 But what are the facts ? The displacement is 

 greatest at the inner edge, pro\-ing that the motion 

 is there greater than at the outer edge. Thus for 

 ever the idea of solidity is disposed of, and it may 

 be taken as, to all intents, proved that the rings 

 are really composed of a multitude of tiny bodies 

 pursuing their course around the planet. It must 

 be conceded that our knowledge of Saturn and his 

 system has been definitely advanced. 



60, Lii-.tha'.'. Road, Lcn.ioH, .Y.£.; August, 1S96. 



SUBDIVISION OF CLOSTERIUM 

 LUNULA. 



By H. E. Griset. 



T X addition to the true conjugation of those 

 beautiful unicellular algae, the Desmidiaceas, 

 by the mutual action of two individual fronds and 

 the resulting sporangium, there is the vegetative 

 multiplication by duplicative subdivision which 

 continually takes place throughout the warmer 

 months of the j-ear in the mature cells or fronds. 

 In this state they appear from time to time on the 

 slide under the microscope, and it is generally 

 conducted with great rapidity. This seems to 

 vary according to the temperature, as may be seen 

 from the following notes, which may, perhaps, be 

 useful to those who have not been fortunate enough 

 to have witnessed this curious and instructive 

 phenomenon. 



The sub-lunate fronds of Closterium lunula, when 

 about to undergo this transverse subdivision, ex- 

 hibit at first an infolding of the walls of the cell 

 at the middle. This constriction continues to 

 increase until the priman,- frond is completely 

 divided into two similar halves, which takes 

 several hours. They generally become detached 

 by a jerking of one of the new cells — the active one, 

 (fig. I, a), while the other remains passive (b) ; or 

 they continue to slowly swing from side to side. 

 The half-fronds are horn-shaped and roimded at 

 the newly-di\ided end, near where the green 

 endochrome at this time presents a deep con- 

 striction, and the internal movements of the parietal 

 protoplasm will be seen to be very active, present- 

 ing numerous little shadowy waves, which carry the 

 round particles along with them ; some of these 

 ultimately become enclosed in the vacuole which 

 has in the meanwhile been formed in the rounded 

 end of the cell ; one of the new cells did not form 

 this vacuole until fifteen minutes after the other 

 (the passive onei, the protoplasmic currents simplj- 

 proceeding round the end, which had pre\'iously 

 been the case with the other cell. 



Fifteen minutes after the perfect di\-ision of the 

 frond (as seen in fig. i) the new cells were elongat- 

 ing and tapering at the extremities, the rounded 

 ends having become decidedly pointed and the 

 active frond had formed the vacuole at its new end ; 

 the constriction of the endochrome was greatly 

 augmented, the vacuole of the passive cell still 

 contained two and that of the active cell one 

 granule (fig. 2). 



Twenty minutes from the perfect division, or 

 five minutes later than the preceding, the cells 

 continued to lengthen and the vacuoles of the 

 passive and active fronds contained three and two 

 granules, respectively (fig. 3). Thirty minutes 

 after the perfect di^-ision the extremities of the 

 new fronds w-ere almost equal in shape, the 



