588 



SUMMARY OF CURRENT RESKARCHES RELATING TO 



technique initiated by H. V. Wilson. The Hydro-ids were cut in pieces, 

 and pressed through bolting silk, 50 meshes to the inch, with the result 

 that isolated cells and small cell aggregates were obtained : these soon 

 aggregated together to form compact masses, and in from 12 to 18 hours 

 a perisarc was secreted by a definite layer of ectoderm cells. The 

 endoderm cells form definite tubules similar in structure to the coenosarcal 

 tubules continuous with the enteric cavities of the normal hydranths. 

 The masses were kept alive for at least 60 days. No sign of cell division 

 was ever noticed, and hydranths never regenerated. 



Microchemical Detection of Aluminium.* — According to E. Kratz- 

 mann, characteristic crystals of caesium alum are obtained when a drop 

 of a solution containing an aluminium salt is mixed on a Microscope 

 slide with a drop of a reagent consisting of equal volumes of a 2 mol. 

 caesium chloride solution and an 8 mol. sulphuric acid solution. As 

 little as 0*001 mg. of aluminium nitrate may be detected by the test. 

 Plant ashes may be tested directly, but the addition of sulphuric acid 

 is recommended when much calcium carbonate is present. The crystals 

 are also obtained when sections of plants are treated with the reagent. 

 Aluminium is of very frequent occurrence in plants, but the " alumina 

 grains " mentioned by Radlkofer and Welmert as being present in the 

 leaves of Symplocese could be identified as aluminium compounds only 

 in the case of S. lanceolata and S. polystachya. 



Metallography, etc. 



Growth of Metallic Eutectics.f— F. E. E. Lamplough and J. T. 

 Scott have sought to determine the effect of under-cooling at the beginning 

 of solidification of the eutectic on the structure of lead-tin, cadmium-tin, 

 and many other binary alloys. No relation could be discovered between 

 under-cooling and the formation, around the primary crystals, of a halo 

 or envelope of the second constituent, separating the primary crystals 

 from the banded eutectic. Under-cooling almost always occurred when 

 care was taken to prevent surface oxidation. Whilst in some cases 

 considerable supervision existed without the formation of such structures, 

 in others marked halos were accompanied by slight superfusion only. 

 When superfusion at the moment of eutectic formation was prevented, 

 either by inoculation, or by shaking, the formation of the envelope was 

 in no way affected. By quenching at various stages in the formation of 

 the eutectic, it was ascertained that in some cases the growth of the 

 eutectic originated at the primary crystals, while in other cases the 

 growth of the eutectic was independent of the primary crystals. The 

 halo appeared to be formed around a primary crystal when the eutectic, 

 originating independently, had reached the primary crystal in its growth. 

 The solidification of the eutectic at this point consisted in the deposition 



* Journ. Chem. Soc, cv. and cvi. ii. (1914) p. 678. 



t Proc. Roy. Soc, Series A, xc. (1914) pp. 600-4 (4 figs.). 



