320 RECORD OF CURRENT RESEARCHES RELATING TO 



having the filament twisted several times on its own axis, so as to 

 resemble a corkscrew. Herr Zukal states that the oscillatory motion 

 which the filaments possess, in common with other members of the 

 family, but more distinctly than in any other genus, consists in a slow 

 torsion of the entire helix round its own axis. If the motion is 

 suddenly interrupted, the filaments become for a moment stationary, 

 and then retreat towards the central point of the movement, forming a 

 dark green lump. The movements are stated by the writer to be 

 obviously and intimately connected with the growth of the alga ; 

 having in fact a close analogy to the well-known rotation of growing 

 shoots and tendrils. The cause of the corkscrew-like torsion is the 

 more rapid growth in length of the filaments than that of the ideal 

 axis of growth. SpiruUna retains its colour for years in glycerine, 

 which seems to indicate that the colouring matter is something different 

 from the ordinary mixture of chlorophyll and phycocyan. 



MICEOSCOPY, &c. 



Method of making^ Sections of Insects and their Appendages.* 



Mr. J. W. Hyatt, President of the New York Microscopical Society, 



says that how to make a section through hard, chitinous organs, con- 

 sisting of several pieces, such as stings and ovipositors, sufficiently 

 thin to allow of examination by transmitted light, and at the same 

 time retain all the parts in their normal position, was a problem that 

 for several years defied all his attempts to solve by any process on 

 record. After many fruitless attempts by other devices of his own, 

 the following very simple method has proved entirely successful. 



The insect or organ is placed in alcohol until it is thoroughly 

 permeated, and then removed to a clear alcoholic solution of shellac, 

 in which it may remain for a day or two. Fit a cylinder of soft wood 

 into the well of the section-cutter ; split this cylinder through the 

 middle, and cut a groove in one or both of the half cylinders, suffi- 

 ciently large to admit the object without pressure ; put the two pieces 

 together with plenty of thick shellac, and tie them with a thread. 

 When the shellac is quite hard, which will be the case in a day or 

 two, place the cylinder in the section-cutter, and after soaking the 

 wood with warm water, sections the ^i^j of an inch in thickness, or 

 less, may readily be made. 



Should the shellac prove so opaque as to interfere with a proper 

 examination, a drop of borax solution will immediately remove this 

 difficulty. 



Collecting and Mounting Spiders' Webs.t — Several methods have 

 been suggested for preserving and mounting spiders' webs. One 

 method was to take the web direct upon a slide having a cell fixed 

 upon it, and at once proceed to mount it. It is, however, very difficult 

 to secure the exact portion of the web you wish, it not being so well 



* ' Am. M. Micr. Journ.,' i. (1880) p. 8. 



t ' Journ. Quek. Micr. Club,' v. (1880) p. 10. 



