ON THE ECONOMY OF CLOSTERIUM LUNULA. 55 



knowletlge. 1 liave devoted now lor some months, and on an 

 average several hours almost daily, to t!ie studj of some of the 

 Desmidiese, esj)ecially the Closteriiun Lunula. With increased 

 objective powers and the use of improved methods of illumi- 

 nation, I have arrived at results which may, I think, interest 

 many of your readers. 



As to the Closterium Luuula, I have ascertained that the 

 best view of its circulation and the cilia which gives it its 

 impulse, is obtained by the use of full sunlight transmitted 

 through the combin.ition of coloured glass, proposed by 

 Mr, Rainey, and adapted to an achromatic condenser. I have 

 used a l-6th objective of Ross's, his l-4tli with the Rainey 

 moderator as illuminator. In diagram A, 1 have given a 

 rough sketch of a specimen of the C. Lunula ; with the 

 above arrangement of the microscope, using also a deep eye- 

 piece, 1 have again and again seen the cilia in full action along 

 the edge of the membrane which encloses the endochrome ; 

 I have seen them also, but not so distinctly, along the inside 

 of the edges of the frond itself. Their action is precisely, to 

 my eye, the same as that in the branchia3 of the mussel. 

 Tliere is the same wavy motion, and as the water dries up 

 between the glasses in which the specimen is enclosed, the 

 circulation gets fainter at the edges, and the cilia are seen 

 with more distinctness. 



In the diagram, I have drawn a line at Z* to a small oval 

 mark ; these exist at intervals, and more or less in number 

 over the surface of the endochrome itself, beneath the mem- 

 brane which invests it. They seem to be attached by a small 

 pedicle, are usually seen in motion on the spot to which they 

 are thus fastened ; from time to time they break away, and are 

 carried by the circulation of the fluid, which works all over 

 the endochrome, to the chambers at the extremities, there 

 they join the crowd of similar bodies, each in action within 

 those chambers, when the specimen is a healthy one. 



The circulation, when made out over the centre of the 

 frond, for instance at a, is in appearance of a wholly different 

 nature from that seen at the edges. In the latter, the matter 

 circulated is in globules, passing each other, in distinct lines, 

 in opposite directions ; in the circulation as seen at a, the 

 streams are broad, tortuous, of far greater body, and passing 

 with much less rapidity. To see the centre circulation, I 

 have used a Gillett illuminator and the l-6th power, so working 

 tlie tine adjustment as to bring the centre of the frond into 

 focus ; then almost losing it by raising the objective ; after 

 this, with great care working the milled head till I just 



