232 



NATURE 



[April 22, 1920 



Dr. H. S. Allen, was originally expounded by Mr. 

 A. L. Parson (Smithsonian Miscellaneous Collections, 

 vol. Ixv., p. I, 1915). The advantages of such a 

 theory were ably expressed recently by Dr. Allen in 

 an opening address before the Physical Society of 

 London. • ' A. E. Oxley. 



The British Cotton Industry Research 

 Association, io8 Deansgate, Man- 

 chester. 



Aquarium Cultures for Biological Teaching. 



The increase in the number of students in biology 

 during the last few years has created a demand for 

 large quantities of such animal types as Amoeba, 

 Actinosph£erium, brown Hydra, and Daphnia. It is 

 often very difficult to obtain to time vast numbers of 

 these types; for in Nature the supply is exceedingly 

 precarious, depending as it does on conditions which 

 are constantly fluctuating. In endeavouring to secure 

 a continuous and plentiful supply of Amoeba proteus, 

 I have accumulated a certain amount of experience in 

 aquarium-keeping on a large scale, the results of 

 which will be useful to others who, like myself, have 

 to deal with large numbers of students. 



Information with regard to Amoeba culture has 

 already been given in " Notes on the Collection and 

 Culture of Amoeba proteus for Class Purposes " (Proc. 

 Roy. Phys. Soc. Edin., vol. xx., part 4, p. 179). 

 Since the publication of that note, however, I have 

 tried, as an alternative plan for procuring the material 

 necessary to inoculate a culture, a modification of 

 the respective methods described by J. B. Parker (" A 

 Method of Obtaining a Supply of Protozoa," Science, 

 N.S., vol. xlii., No. 1090, p. 727, 1915), Libbie Hyman 

 (Journ. Exp. ZooL, vol. xxiv.. No. i), and Asa A. 

 Shaeffer (ibid., vol. xx., No. 4), and with success. 



Water from such places as the drainage-cuttings in 

 birch, alder, and willow woods, or from the margins 

 of ordinary pools and ponds, together with the fila- 

 rnentous algae and the brown scum and included 

 diatoms overlying the. dead leaves and the other 

 decaying organic matter forming the floor of such 

 places, is gathered in autumn or in early spring. 

 This is allowed to stand in tap-water for some time, 

 until a rich brown scum appears on the top. The 

 top water with the scum is poured off into another 

 glass vessel, and wheat is added (i gram to a litre of 

 water). In Februarv minute Amoebae begin to rfiake 

 their appearance ; these become fully grown in May 

 and June, and will then divide rapidly, forming a 

 luxuriant culture until the late autumn. When encyst- 

 ment of most individuals again takes place. 



Once started. Amoeba cultures require no further 

 attention than a supplv of water to" compensate for 

 evaporation, and the addition of wheat from time to 

 time. 



I am indebted to Prof. Bourne, of Oxford, for 

 information that boiled rain-water can be used in 

 those districts, e.g. Oxford, where the tap-water con- 

 tains much mineral matter. 



Actinosphaerium. — Mv principal difiicultv in the 

 culture of Actinosphp^ria has been in main- 

 taining for them a sufficient food-supply. Stentors 

 and ^ vorticelloids, their favourite food, appear to 

 require running water, and therefore quickly die 

 off when introduced into the laboratorv (except 

 the green stentor, which thrives well when once 

 established, and a small vorticelloid which appears 

 in infusions of certain pond-weeds). The common 

 rotifer is an excellent food, and this can be ob- 

 tained from rubbish left over from pond-gatherings 

 by means of wheat or hay infusion. Members of the 

 familv Cathvpnadae (especially Monostyla, which is of 

 NO. 2634, VOL. 105] 



frequent occurrence in Amoeba cultures, and there- 

 fore easily grown in wheat-water) are the most useful 

 of the above-mentioned foods. 



Since Actinosphaeria disappear very quickly when 

 their food is exhausted, and since, on the other hand, 

 they grow and multiply very rapidly when the food- 

 supply is good, and very quickly exhaust this food- 

 supply, it is necessary to give the Rotifer culture a 

 good start before irtroducing the Actinosphaeria into 

 it. In practice I have several Monostyla cultures in 

 readiness, and then, about three months before requir- 

 ing large numbers of Actinosphaeria, I inoculate one 

 or more of the Monostyla cultures with a few Actino- 

 sphaeria and set the jar aside. These latter soon 

 multiply and appear in myriads. 



Hyrfra.— Large brown Hydra showing buds and 

 reproductive organs can be obtained in considerable 

 numbers and very quickly in laboratory cultures 

 (especially in rooms with a fairly uniform temperature 

 of 60° F.) if they are systematically fed on a generous 

 diet of Crustaceans, which latter can be obtained by 

 the culture gf Daphnia. The Daphnia should be 

 strained off by means of a small net, and a concen- 

 trated mass of them in a small quantity of water 

 should be added periodically to the jar containing the 

 Hydra. Several hundreds of Hydra by this means 

 can be obtained from one or two individuals in a 

 few weeks. 



Interesting colour-changes, varying from dingy 

 brown to a bright pink, can easily be effected in 

 brown Hydra by varying the Crustacean diet. 



Daphnia. — I am indebted to Mr. P. Jamieson for 

 the discovery of the value of small pieces of earth- 

 worm for the cultivation of Daphnia. If an infusion 

 of dead earthworms in water be allowed to stand in a 

 warm place (i.e. near the radiators in the laboratory) 

 it is quickly converted into a rich food, which can be 

 added to the Daphnia cultures, as required. A few 

 Daphnia introduced into a large wide-mouthed glass 

 bottle or beaker of water, to which the worm-water 

 is regularly added, very quickly multiply. Several 

 of these cultures should be kept going if the cultiva- 

 tion of Hydra is very intensive, as they must be 

 allowed to recuperate after they have been depleted 

 by use. 



A variety of other Protozoa, Crustaceans, Oligo- 

 chaetes, etc., make their appearance in the above- 

 mentioned cultures, commonly sufficient to supply 

 abundant material for demonstration purposes. 



Monica Taylor, S.N.D. 



Convent of Notre Dame, Glasgow. 



lonisation in the Solar Chromosphere. 



It is well known that the spectrum of the upper 

 layers of the solar chromosphere is chiefly composed of 

 those lines which are relatively more strengthened in 

 the spark than in the arc, and which Sir Norman 

 Lockyer originally styled enhanced lines. The best- 

 known examplcTs are the calcium H and K and the 

 strontium pair (4216, 4077). According to modern 

 theories of spectral emission, these lines are due to an 

 atom which has lost one electron. The principal line 

 due to the normal atom of calcium is the ^-line 4227, 

 and the corresponding Sr line is 4607, both of which 

 occur at much lower levels. According to modern 

 theories, therefore, Ca, Sr, and Ba atoms are more 

 and more ionised as we approach the upper layers of 

 the solar atmosphere, while in the lower lavers both 

 normal and ionised atoms occur. 



If we assume that ionisation is a sort of reversible 

 chemical process taking place according to the scheme 

 Ca^-Ca+ -1-^- U, where e is the electron, Ca+ is a 

 positively charged Ca atom, and U is the energy of 



