454 



KX(1\VLEDGE. 



November. 1910. 



to the surface of the water, forming, in all probability. 

 Nature's most ingenious device for the escape of an insect 

 from surroundings that have become unsuitable. Professor 

 Miall gives a spirited description of this act in his book, which 

 is well worth reading by those who \\ ish to pursue the subject 



f'"'''^^''- .\KTHl-K C. BAXFIELD. 



BATRACHOSPERML'M ATRCM (L~)ill\v.) H.ARV.— 

 At a recent meeting of the OueUett Microscopical Club, 

 Mr. Higginson exhibited a 

 mounted specimen of the 

 abo\e. It was found grow- 

 in,< on the brick-work of a 

 weir at Colnbrook. in May. 

 This species is not nearly 

 so familiar as the common 

 B. iiioiiilifonuc. Roth., in fact 

 many would scarceU- recognise 

 it at first sight as belonging to 

 the same genus. The branches 

 which are the salient feature 

 in B. iiionilifornie are here 

 reduced to the smallest dimen- 

 sions, as shown in the illustra- 

 tion. Figure 1, which is from a 

 photograph by Mr. Banfield 

 of a mounted specimen. Dr. 

 Cooke describes it (British 

 Freshwater Algae, p. 292) as 

 " vaguely and much branched, 

 whorls abbreviated, distant ; 

 interstitial branchlets very 

 short, one or two celled." 

 Ouoting Hassall. he says: 

 '■ The articulations, or inter- 

 nodes, may be compared to 

 reversed cones, the superior 

 part or whorls being formed 

 of a few short, simple subu- 

 Late filaments, which are not 

 beaded. That portion of each 

 articulation which is below 

 the whorl is transparent, and 

 beautifully exhibits the tubular 

 and jointed structure of the 

 layers which invest the prim- 

 ary cells in all the species of 

 the genus Batracliosperiniiiir, 

 from many of these tubes short 

 branches are gi\en off which 

 have almost the appearance 

 of scales." 



At a later date Mr. Higginson 

 had the good fortune to find on 

 the shell of a pond snail another 

 specimen which appears to 

 agree exactly with the variety named by Dr. Cooke, Dillcini. 

 In describing it, he says: " F'ilaments Aery thin, lower nodes 

 remote, the interstices beset very densely with prominent cells, 

 upper nodes crowded, branchlets very short, consisting of three 

 to four cellules, extreme apical nodes confluent." In a note, he 

 says: "This is usually considered as a variety of B. va^iiin. but 

 it seems more closely allied to B. atriini, if that be really a 

 distinct species." In this latter specimen the features Dr. 

 Cooke describes are very distinct ; what he speaks of as 

 "prominent cells" ax^e very numerous, and in several cases 

 show short branches, but they cannot be mistaken for the 

 actual branches Iwhich occur at the nodes! and are obviousK- 

 only proliferations of the cortical cells which envelope the 

 internodes. There are several cystocarps on this example. 

 The colour of the lixing plants was much masked by the 

 presence of numerous diatoms and other epiphytes, as is so 

 commonly the case with this genus ; in the mounted specimens 

 it is a clear pale green, but that is largely due to the mounting 

 medium. In the figure the irregular projecting thre;ids are 

 epiphytes, chiefly diatoms, mostly Syncilnr. i jj 



Figure 1. 

 Bat rachuti[>criii II III at ruin 



A M1:TH()D in MICRO-TECHNIQUE.— In the 

 Zcitschrift fi'ir wissciiscliaftliclic Mikniakopic. Bd. XXVH, 

 Heft. 2 (Aug. 1910) there are some notes on microscopical 

 technique by J. T. Wilson, F.R.S.-, Professor of .\natomy in 

 the University of Sydney, in which he gives the following 

 details of a convenient and simple expedient for suspending 

 blocks of tissue in fluid, and more especially for passing them 

 through successive series of fluids. He uses short segments of 

 glass tubing from ISmm. to iOnnn. in diameter, one end of which 



is closed by means of fine net 

 tied round it ; the tissue is 

 placed in the tube, which is 

 then closed at the other end 

 by a perforated cork of suffici- 

 ent size to float the whole in 

 the fluid. Such a floating 

 vessel can be transferred from 

 one fluid to another with the 

 utmost readiness, and with- 

 out, in any way. handling the 

 tissue. Similar arrangements 

 have been described before, 

 but this has the merit of very 

 great simplicity and cheapness. 

 If the gauze bottom of the 

 tube, prepared as above de- 

 scribed, be dipped in a 10 per 

 cent, solution of gelatine and 

 allowed to set. it can then be 

 formalinised and preserved 

 indefinitely either in very weak 

 formalin or in alcohol. Such 

 a tube may be utiHsed as a 

 floating dift'erentiator. Thus, a 

 piece of tissue may be placed 

 in it in a small quantity of 

 one fluid, and after inserting 

 the perforated cork it may be 

 floated in a vessel containing 

 another fluid, thus securing a 

 ver)- gradual diffusion of one 

 fluid into the other through the 

 gelatine membrane. 



MICROSCOPICAL APPA- 

 R.\TUS. — The first section, of 

 more than twenty pages, in Mr. 

 C. Baker's new classified list 

 of second-hand instruments is 

 devoted to microscopes and 

 accessories of all kinds, and 

 of verj- special interest is 

 the sepai'ate list of apparatus 

 that belonged to the late Dr. 

 Dallinger. It contains many 

 interesting items, among which 

 IS a water immersion objective of one-fiftieth of an inch focus, 

 by Powell & Lealaud. — We have before us also the first 

 catalogue of second-hand apparatus issued by Messrs. Angus 

 and Company. .As said in the preface, the possibility of acquiring 

 apparatus at a cheap rate may be a real boon to those who 

 wish to try experiments at the least possible cost. — We^ ad\ise 

 our readers to get a copy of the little booklet entitled, " Some 

 Hints on the use of the Shding Microtome for the Paraffin 

 Method," which has been issued by Mr. E. Leitz. and which 

 contains some very useful information. 



SECTION OF KIDNEY. — We are able, by the courtesy 

 of the Bausch & Lomb Optical Coy., of Rochester, U.S.A., 

 to publish a reproduction in half-tone of a photograph of a 

 cross section of an entire infant's kidney, under a magnifi- 

 cation of 7 diam. This beautiful photograph was taken by the 

 Bausch & Lomb-Zeiss Micro-Tessar 72 nnn. ; a special 

 condenser was used. The slide was stained with Eosin and 

 Haemoto.xylin. The reproduction illustrates, in a measure 

 onlv, the excellence of the original jihutograph. 



