1086 SUMMAEY OF CUREENT RESEARCHES RELATING TO 



mislead, were it not for the abundant cellulose plugs which occur 

 only in the tubes. 



In the study of the ovules material fixed in strong alcohol, in a 

 saturated aqueous solution of picric acid and in chrom-acetic acid,* 

 was used. The contraction of the contents of the embryo-sac is un- 

 avoidable. Prof. Barnes thinks the alcoholic material is quite equal 

 to the others and less troublesome. He found it necessary to depend 

 on getting chance sections of the ovules by cutting the whole ovary 

 longitudinally and laying tbe sections in glycerin. Previous to tbe 

 cutting, the material is placed in alcohol glycerin for twenty-four 

 hours or more. After being mounted in glycerin tbe sections become 

 clearer and clearer. He also tried cutting sections in various known 

 directions, by imbedding the ovules in coloured pith to render them 

 more easily seen. The results, on the whole, are not better than by 

 depending on chance sections, and they are much more troublesome. 



Imbedding in Paraflfin.f — Dr. E. Selenka has devised a method 

 for fixing minute objects in a definite position in paraffin. 



In a thin- walled glass tube (fig. 251) a central depression of 

 limited extent is formed by heating this portion, closing one end of 

 the tube with the finger, and sucking at the other end. One open 

 end of the tube is then connected with a T-piece, one arm of which 

 is in communication with a vessel of warm water, the other with a 



Fig. 251. 

 A 



i 



^ 



vessel of cold water ; the other end of the glass tube permits the 

 water to flow out into another vessel. The paraffin is poured in a 

 melted condition into the depression A on the glass tube, which is 

 previously warmed by passing hot water through it, and the object to 

 be imbedded is arranged under a lens ; cold water is then admitted, 

 and the object is fixed in the desired position. 



Andrews and Nachtrieb's Water-bath. | — The following is a 

 description of a water-bath planned by Mr. E. A. Andrews and 

 Mr. H. E. Nachtrieb, which has been in use for some time in the 

 biological laboratory of the Johns Hopkins University. 



The bath proper consists of a closed copper cylinder 28 in. in 

 diameter and 8 in. deep. To the borders of holes cut in the top are 

 soldered four round, flat-bottomed basins, 8 in. in diameter and 4 in. 

 deep, with a distance of 2 in. between the nearest points of any two 

 basins; and nearer the edge of the top, at the angles between the 



* Chromic acid 0*7, acetic acid 0*3, distilled water 99. Strasburger, loc. cit., 

 p. 328. 



t Zool. Anzeig., viii. (1885) pp. 419-20 (2 figs.). 

 t Amer. Natural., xix. (1885) pp. 917-9 (3 figs.). 



