and Laboratory Methods. 2289 



metallically clean ; fine emery cloth should be used on them until they are free 

 from lacquer, oil, etc. (2) Vibrations should be avoided. Mount the apparatus 

 on a steady table and handle the screw delicately in taking measurements. 

 Any cell will do for the circuit and any telephone receiver will act, though a 

 " loud speaker " is most convenient. For resistance a few hundred ohms serves, 

 its object being to keep the current small, but it is not an essential. Any spare 

 screw on the microscope serves for completing the circuit or simple lashing to 

 an unlacquered surface works. 



This electric micrometer has the advantage of being a direct method, thus 

 giving surer results than eyepiece micrometers. It is more enduring than the 

 stage with a graduated screw movement, since the work of carrying the stage 

 does not rest on the micrometer screw, causing wear ; a larger disc can be used 

 without inconvenience, and the apparatus put away when not in use. No diffi- 

 culty has been experienced in reading to \ micron, and with the insertion of 

 a capstan-pin into the edge of the milled head of the screw, a more delicate 

 angular movement may be given to the screw, and readings of Jg micron 

 obtained. a. m. c. 



Blackman, M. W. Methods in the Preparation The material was obtained from a 



of Material for Study of Spermatozoa of . r o i i i • i • r i 



Myriopods. Kansas University Quarterly, species of Scolopendra which IS found 

 10: 2, 1902. abundantly in the Southwest. In the 



manipulation of the material two fixing reagents were used : Flemming's chrom- 

 osmium-acetic mixture and Gilson's nitro-acetic-sublimate mixture. Both of these 

 mixtures gave excellent results, but Gilson's fluid was the better. The fixation 

 with this was perfect, there being no shrinkage or other apparent distortions. 

 The only disadvantage of the Gilson fixative is the difficulty experienced in the 

 later manipulation. When embedded in paraffin the material is so soft and 

 spongy that it folds upon the knife in cutting. This difficulty was obviated in 

 the following manner : The material was gradually carried up to absolute alco- 

 hol, from which it was transferred to celloidin and allowed to infiltrate thoroughly. 

 Then the celloidin was allowed to evaporate gradually, until it was of the con- 

 sistency of thick cream. Finally all the surplus celloidin was removed, and the 

 mass cleared for several hours in chloroform. This accomplished, the specimen 

 was infiltrated with paraffin and embedded in the same substance. The material 

 cut perfectly, without any wrinkling or distortion of the sections, and without any 

 of that shrinkage of the cells which often occurs when the ordinary paraffin 

 method is employed. In staining, a considerable number of reagents were em- 

 ployed. The best results were obtained with Heidenhain's iron-haematoxylin, 

 used either alone or in connection with Congo red ; Keruschwarz ; and the 

 Flemming three-color stain. Fair results were obtained also with Bismarck 

 brown, methyl-green, cyanin, and Auerbach's methyl-green, and acid fuchsin. 



c. w. J. 



