ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 709 



stitutc, and has used it for some time with most satisfactory results. 

 The following is tbo method employed in the preparation of very 

 delicate objects. 



After having removed the water from the object in the usual 

 manner by alcohol, it must be laid for a short time in pure chloroform, 

 until it is completely saturated. The object is then placed in a 

 solution of paraffin in chloroform which is so made that it is fluid at 

 a temperature of 30-49° C, but firm at a moderate temperature. To 

 retain it in a fluid state while the object is in it, it is sufficient to place 

 it in lukewarm water. The author prefers a solution of paraffin in 

 chloroform saturated at 35° C. In this the object is placed until it is 

 thoroughly impregnated with the solution, for which ^-1 hour is 

 sufficient. The object is now placed in a watch-glass with a little of 

 the solution, and the chloroform is completely evaporated at a very 

 moderate temperature (40-50° C), which is sometimes a long process 

 as the chloroform escapes very slowly when mixed with paraffin. 

 Larger objects can be transferred direct from the solution into melted 

 paraffin in the same way as in using the mixture of paraffin and oil 

 of turpentine. For delicate objects which must be completely and 

 uniformly saturated with paraffin, the first method is in any case more 

 to be recommended. Complete evaporation of the chloroform is also 

 a necessity, for the presence of even a small quantity is apt to make 

 the paraffin very soft. To make the sections the object can either be 

 poured with the melted paraffin upon a small piece of paraffin, or 

 after it has been placed in a larger mass of melted paraffin, it can be 

 poured into a paper box in the usual manner. 



This mode of imbedding is the most harmless and effective which 

 the author has hitherto employed. Both object and paraffin form 

 a thoroughly compact mass, which can be cut exceedingly uniformly. 

 The paraffin which remains after the evaporation of the chloroform 

 is of a very uniform structure without any tendency to crystalliza- 

 tion, which very much favours the making of thin sections. With 

 careful manipulation a thorough filling of the smallest inter- 

 stices of the object can be effected, and there need be no apprehension 

 of shrinking or brittleness. 



The author (who acknowledges the assistance of Dr. F. Bloch- 

 mann) mentions some of the cases for which they have found the pro- 

 cess very successful, viz. Amphioxus, Cerianthus, tape-worms, ambulacra 

 of Echini, decalcified ambulacra of Holothurians, gelatinous parts of 

 Cteuophora, Hydroid polyps, &c. Of large objects, such as cross- 

 sections of Amphioxus and Cerianthus, sections can be made without 

 difficulty of yi^y mm. in thickness. Of small objects, as the tentacles of 

 Cerianthus, or entire Hydroid polypi, sections can be made of o ^ mm. ; 

 if Thoma's microtome is used, indeed under some circumstances 

 even to ^J-^ mm. if the knife be placed rather obliquely to the 

 object. 



Perenyi's Hardening Fluid* — Dr. J. Perenyi describes a new 

 hardening fluid for embryological purposes which has given surprising 



* Zool. Anzeig., v. (1882) pp. 459-60. 



