lO 



NA TURE 



[July 7, 1923 



As the reviewer referred to, I warmly welcome the 

 remarks of Dr. J. W. Evans on the tendency to 

 modify Greek forms, sometimes beyond recognition, 

 when they are introduced into scientific terminology. 

 I went to some trouble in looking up Gilbert's 

 " epeirogeny," which Sir A. Geikie of course spells 

 correctly in his " Textbook of Geology." I have 

 long clung to " deinosaur," and American authors 

 should bear in mind that the use of an i for ei com- 

 plicates pronunciation when the terms are handed on 

 to other nations. 



The chief offender, however, was Charles Lyell, who 

 knew that he was doing wrong when he wrote his 

 footnote on p. 53 of the third volume of the " Prin- 

 ciples of Geology " in 1833. He justified his 

 " Miocene " and " Pliocene " by the use of " encenia " 

 and " icosahedron " ; but the result has been the 

 absurd American term " Cenozoic," which, if it means 

 anything, should remind us of the emptiness of life. 



The frequent use of the prefix " epi " makes one 

 anxious to preserve " epeirogeny." I wish that we 

 could mark the first e with a stroke to keep it long, 

 and this remark applies also to " Tethys." But in 

 the face of " Epirus," and " Pisistratus," and 

 " Phidias" it is difficult to be logical. May we not 

 attempt, however, as Dr. Evans suggests, to keep our 

 newly invented scientific terminology from degenerat- 

 ing like our common speech ? 



Grenville a. J. Cole. 



On the Significance of "Rings" on the Shells 

 of Cardium and other Molluscs. 



In Nature of February 3, p. 146, I referred to 

 experiments on determining the rate of growth of 

 a fixed population of marked cockles {Cardium edule). 

 In this experiment the box which was fixed in the 

 bed of the River Yealm and contained the cockles 

 was visited monthly, and sometimes at intervals of 

 only a fortnight, for the purpose of measuring the 

 increment in growth since the previous visit. This 

 method of work resulted in an interesting observation 

 on the formation of rings on the shells of the growing 

 cockles. It was found that in the young cockles, 

 i.e. up to about 16 mms. in length, dark rings were 

 formed monthly or fortnightly in a majority of cases, 

 on the shells at the size they were when last measured, 

 but that no similar formation of rings could be 

 detected in the larger and generally older shells. 

 On the other hand, both small and large cockles 

 showed distinct rings after the winter period. 



In young cockles, growing in length at the rate 

 of one millimetre or more a week, a cessation of 

 shell-growth for a few days as a result of being taken 

 out of their habitat and handled is enough to produce 

 a distinct ring, but older cockles which increase 

 in length a very small amount in even a month show 

 no external sign of a small period of cessation in 

 growth. Thus rings on the shells of cockles are 

 undoubtedly due to periods of cessation of shell- 

 growth, and the length of the period necessary to pro- 

 duce an effect depends directly upon the size of the 

 cockle. 



In this connexion it is interesting to read the 

 history of cockles picked up haphazard. Some shells 

 I picked up on the shifting sands of the bar at Padstow 

 showed numerous rings close together, and there 

 is no doubt that these rings can be interpreted as 

 periods of cessation of shell-growth probably separated 

 by only a few weeks, and due to the cockles being 

 embedded deep in the shifting sand after rough 

 weather. On the other hand, cockles picked up in 

 protected situations show mostly those rings v.'hich 

 can be interpreted as winter rings, but often also 



NO. 2801, VOL. 112] 



near the umbo, tiny rings which may mean the 

 occurrence of a disturbance for only a few days 

 while the individual was young. Similar winter 

 rings have been found by experiment in Crepidula 

 and in many cases in Patella, but Patella may not 

 show winter rings in some situations at Plymouth 

 after a mild winter. 



In fishes the indications of periods of growth and 

 of cessation of growth are very important, and in 

 view of the observations mentioned above it would 

 be interesting to know whether the otoliths and 

 scales of young fishes, which show distinct rings 

 (apparently produced in winter and summer), would 

 reflect the effects of short periods of an analogous 

 disturbance in the same way as the shell of the cockle. 



J. H. Orton. 



Marine Biological Laboratory, Plymouth, 

 June 19. 



A Crystallisation Phenomenon. 



The attached photograph (Fig. i , natural size) is of 

 interest, as it illustrates a phenomenon which does 

 not appear to have been recorded. 



For certain experiments it was necessary to purify 

 some samples of salicylic acid, and recrystallisation 

 from hot water was resorted to. The work was 

 carried out in a litre conical flask, and a layer of 

 crystals was formed at the surface of the solution on 

 cooling. Below this layer many crystals were seen 

 to be suspended by threads, and as the photograph 

 shows, one thread would grow several crystals at 

 different depths in the liquid. 



In a bright light, reflection may occasionally be 



observed from some threads, but generally they are 

 too small to be seen with the naked eye. They are 

 elastic in the sense that, if the vessel is gently swung, 

 the crystals oscillate at the end of their threads, which 

 sometimes form flexible loops instead of hanging 

 vertically. The threads are quite stable, as the 

 suspension remains for months at a time. On one 

 occasion the crystal layer was formed on a small 

 grid of glass fibres and the solution syphoned out ; 

 the crystals were left hanging, but the threads could 

 not be distinguished. 



I am indebted to Mr. Sowerby of this College for 

 the photograph. C. R. Bailey. 



Chemistry Department, 



University College, London, W.C.i, 

 June 8. 



