IVlAYsV^^^l 



m 



^ay Avhich of the two views' is supported by the ■dis- 

 covery of the same species in London. Mr. MoriSon 

 assures me that no plants have been introduced into 

 his garden for at least three years. Probably the 

 worm will be found in other parts of London, and 

 it would be worth while to search carefully for ft 

 at Kew. 



It will be remembered that another land Planarian, 

 Placocepkalus {Bipalium) kewense, was first found at 

 Kew and is admittedly exotic, having since been 

 found in many parts of the world, especially in the 

 neighbourhood of botanic gardens, being distributed, 

 doubtless, with plants. There is, however, one un- 

 doubtedly indigenous British land Planarian, Rhyncho- 

 demiis terrestris, which differs from R.Scharffi in its 

 grey colour and much smaller size. This worm is rarely 

 met with unless carefully searched for, and it is quite 

 possible that R. Scharjfi also will yet be found in 

 situations less open to suspicion than Dublin and 

 London gardens. I hope that the publication of this 

 letter may lead to such a discovery. 



Arthur Dendy. 



Zoological Department, Universitv of London 

 (King's College), April 28. 



Method of Cutting Sections of Cotton Hairs. 



No satisfactory method of cutting sections of cotton 

 hairs and similar material appears to have been pub- 

 lished ; the technique recommended by Balls (" De- 

 velopment and Properties of Raw Cotton," p. 176) 

 is open to the objection that the hairs pull away 

 from the wax at the cutting surface, thus losing the 

 rigidity which is essential for good sections, and 

 attempts made to remedy this by coating the hairs 

 with a paraflfin-wax different from that of the main 

 embedding mass did not produce any marked increase 

 in adhesion ; while embedding in celloidin or cellulose 

 acetate gave very unsatisfactory results by reason of 

 the contraction and distortion of the hairs. 



The method finallv evolved was modified from that 

 of Breckner (Z. /. Wiss. Mikr., vol. xxv., p. 29, 1909), 

 and is dependent on the use of a coating of celloidin 

 to procure greater adhesion to the wax embedding 

 mass. The cotton, fixed in a small wire frame for 

 greater convenience, is "wetted out" with absolute 

 alcohol and placed in a dilute syrupy solution of cel- 

 loidin in alcohol-ether, which is allowed to evaporate 

 to half or a third of its volume. The material is then 

 taken out, squeezed between the fingers to remove 

 excess of fluid, and placed in a chloroform solution 

 of paraffin-wax for two hours, after which the cotton 

 is cut from the frame, transferred to paraffin, and 

 quickly embedded. Sections should be cut without 

 delay, as the material appreciably toughens within 

 twenty-four hours, but blocks can be stored in water 

 for an indefinite time if a trace of antiseptic be added. 



Cutting should preferably be done on a sliding 

 microtome, but 5^ sections have been made without 

 difficulty on a Leitz "Minot," with the knife oblique. 

 A useful way of dealing with the sections when cut 

 is to dissolve away the wax and celloidin in alcohol- 

 ether and centrifuge. If the sections are thin enough 

 a very large proportion will be the right way up when 

 spread upon the slide., 



Since this letter was written a description of a 

 method for embedding cotton yarns and fabrics has 

 been published in the Journal of the Textile Institute 

 (.'Xpril, 192 1) by Willows and Alexander. Opportunity 

 has not so far arisen for comparative tests of the two 

 techniques. H. J. Denham. 



Botanical Laboratory, British Cotton Industry 

 Research .Association, Shirley Institute, 

 Didsburv. .April 20. 



NO. 2688, VOL. 107] 



1-'?-^ . An Unknown Organism iii Flint; '*■' ^--^^ 



i", ,.' K^^\, ° <''■,''' ^i'-v:^.^':. 



A' PIT dug in my garden here exposed about .12 ft. 

 of the usual Thames Valley gravels and sands, at 

 which depth (approximately) what local excavators 

 call "shingle " was reached. This is composed chiefly 

 of flint-stones mixed with sand, and lacks the binding 

 properties of the gravel above. The rule is to stop 

 digging for gravel when the " shingle " appears. 



Pending a detailed description which will be given 

 elsewhere, I may sav that the gravels consist of 

 various types of flint and different kinds of sand- 

 stones, together with quartzites, vein quartz, Lydian 

 stone, chert with spicules, fragments of sarsen, etc, 

 some of these being of sufficient interest to warrant 

 the cutting of micro-sections. During the last few 

 vears some hundreds of these stones have been washed 

 and examined by the platyscopic lens and microscope 

 for surface features. 



On one of the flint fragments I discovered a minute 

 fossil organism resembling some form of insect, the 

 like of which, so far as I can ascertain, has not been 

 seen in flint before. There is a head with curious 

 projections on either side, club-shaped antennae which 



Fig. I. — Photomicrograph of an apparent organism in flint. 

 Magnification, about ^o diameters. 



are segmented, a thorax, and an abdomen, but no legs 

 are visible. 



The chitinous parts appear to be silicified, and 

 show up well when moistened under a low power, but 

 there are reasons why it is a very difficult object to 

 photograph satisfactorily in the ordinary way. The 

 one I enclose was kindly taken for me by Mr. A. 

 Cornell with a super-microscope, the magnification 

 being about 30 diameters (Fig. i). 



It is difficult to understand how an organism of 

 such delicate structure could have been preserved iy 

 flint unless its entombment occurred while the flint 

 was in a colloid condition. If any reader of N.ature 

 can say what the organism is,^ I shall feel grateful. 



C. Carus-Wilson. 



Strawberry Hill, Middlesex 



Ocean Tides. 



While not considering myself qualified to question 

 the gain to scientific knowledge on the theoretical side 

 which might accrue from the investigation of ocean 

 tides, such as Prof. Proudman suggested in his article 

 in N.ATURE of April 7, p. 176, I yet venture the opinion 



