croscopy. 



smeared in the same way and the two collodionized surfaces are brought 

 together. The holder and collodion block are now immersed for a few 

 minutes in chloroform, or long enough for them to become firmly 

 united. 



The preparation is now screwed between the jaws of the olject- 

 carrier of the rainotome and covered, by means of a camel's hair brush, 

 with oil of thyme. The minotome knife is flooded with the same oil. 

 The oil, which thus takes the place of alcohol usually used, has the 

 advantage because of its lubricating property, of not only permitting 

 thin sections to be cut, but its slow evaporation allows one to leave his 

 work at anytime for minutes or even hours without the object being 

 injured. 



After a few sections have been cut from the block of collodion, the 

 relative position of the plane of the knife to the axis of the object can 

 be definitely established. I have had no difficulty in orienting small 

 Arthropod embryos by simply examining the object and plane of cut- 

 ting at this time with a compound microscope. The segments, appen- 

 dages and even nuclei being as clearly shown as if mounted in balsam. 



The object, satisfactorily oriented, is now cut and the sections at 

 once transferred to the slides, covered with balsam and mounted, or, 

 if they are not immediately needed, they may be kept indefinitely in a 

 vial of the oil. 



If the sections are to be arranged 'in series,' they are simply placed 

 upon a slide one after the other, care being taken not to flood the 

 slide with oil but to keep it quite dry. After the sections are arraD ged, 

 the slide is tilted up to allow the excess of oil to drain away, fifteen 

 minutes generally being sufficient. Balsam is now placed on the 

 sections and a warm cover is allowed to gently foil over the series, no 

 section of which ought to leave its place. 



The above method is especially useful in the preparation of larger 

 yolk-bearing eggs.— H. C. Bumpus, Brown University, Prov., h. 1., 

 Dec, 14, 1891. 



Imbedding Blastoderm of Chick in Collodion.^-For sec- 

 tioning, blastoderms should be dehydrated, either before or after 

 staining, as is thought best, and immediately transferred to a tnm 

 solution of collodion 2 (2 per cent.,) after which they are placed in a 



'Gage & Hopkins, Proc. Am. Soc. Microscopist, 1890, pA* n ^ ^ fe 





