2070 



Journal of Applied Microscopy 



they are killed by a fixing fluid, which at the same time sticks the egg to the 

 alga. The objects are in this process not oriented, yet this method can profit- 

 ably be used for our purpose. Schydlowski recommends a thin plate of photo- 

 xylin to stick objects on. Under B, I can mention only Samter's method.^ In 

 this the shell membrane of a hen's egg is used as substratum, and fish-glue as 

 the fixative. Under C, we can consider Patten's simple but excellent method, ^ 

 and its modifications by Woodworth^ and Hoffmann^. Patten and Woodworth 

 use a slip of writing paper (" linen cloth ") to fasten the object on, while Hoffmann 

 prefers a small piece of glass. Lately Drew^ has improved Patten's method in 

 first draining ofif the superfluous oil on an inclined plane of tracing linen. Jor- 

 dan^ fastens the objects on a movable metal sphere coated with resin. A gela- 

 tine plate is used in Field and Martin's complicated method^. Apathy^ also 

 uses a gelatine plate to give a guide line on the celloidin block, although he does 

 not stick the object on the gelatine plate. Halle" recommends for the same 

 purpose a plate of hardened white of egg. There may be other similar devices 

 which are not as yet made public. 



The method I am about to describe is simply a modification of Patten's 

 method, in which C7z'a is substituted for writing paper. The reason I prefer 

 the alga to paper, we shall see later. My present account is, therefore, mainly 

 a repetition of Patten's, yet I think the CZ/va method, described at length, will 

 be found of use by the reader who is not familiar with this line of technique. 

 There are two things which should be at hand before orienting small objects by 

 this method ; one, a small piece of preserved CZ/7>a, the other, celloidin-clove-oil. 



C//va can be obtained readily in any quantity between tide-marks, as a 

 " by-product " of summer collections. The alga should be kept in 70 per cent, 

 alcohol until all the chlorophyll comes out. By changing the alcohol several 

 times this will be quickened. After being bleached the i^va fragments should be 

 stained slightly with borax carmine. A small rectangular piece is cut out from 

 the stained C77>a, the size depending upon the number of objects to be arranged 

 on it. After a thorough dehydration in absolute alcohol the pieces are clarified 

 by adding xylol drop by drop, and are preserved in clove oil. It is advisable to 

 have at hand many of these pieces of various sizes ready for use. 



To make the solution of celloidin in clove oil a vial should be partly filled 

 (about one-fifth) with granulated celloidin and then completely filled with clove 

 oil. The vial is placed on the paraffin bath for a few hours and shaken several 

 times during heating. By doing so, not only is solution of the celloidin accel- 

 erated, but the water in the clove oil, if present, is also driven out. 



Just before imbedding, a piece of Ulva prepared as above is taken out and 

 pressed between the thumb and finger until it becomes perfectly flat. The Ulva 



^Samter, M. Zeit. wiss. Mikr. Bd. 13, pp. 441-446, 1897. 



^Patten, W. Zeit. wiss. Mikr. Bd. 11, pp. 13-15, 1894. 



3 Woodworth, W. M. Bull. Mus. Comp. Zool. Vol. 25, pp. 45-47. 1893. 



^Hoffmann, R. W. Zeit. wiss. Mikr. Bd. 15, pp. 312-316, 1899. 



^Drew, G. A. Zool. Anz., Jg. 23, No. 611, pp. 170-174, 1900. 



''Jordan, H. Zeit. wiss. Mikr. Bd. 16, pp. 33-37, 1899. 



■^Field and Martin. Zeit. wiss. Mikr. Bd. 11, pp. IT-12, 1894. 



* Apathy. Zeit. wiss. Mikr. Bd. 5, p. 47. 1888. 



■'Halle. Zeit. wiss. Mikr. Bd. 12, p. 365 (Referat), 1895. 



