November 25, 1922] 



NA TURE 



701 



formula q/6 . 156, while other lines which are of 

 vanishingly small intensity in comparison with it 

 are assigned formulae with much smaller quantum 

 numbers. For example, the doublet at X3652, which 

 is the seventh in the sharp series and so faint that 

 it fails to appear in the photographic reproduction 

 of the spectrum, is assigned the formula 6 \ .9/5. 

 Similarly, the first diffuse singlet at \6678 gets the 

 formula 9/6 . 24/7, while the fifth in the same series is 

 indicated by 7/5 . 10/5, that is, by much smaller 

 quantum numbers, while it is actually a far fainter 

 line than the other. 



These facts naturally lead one to question whether 

 Dr. Silberstein's proposed new combination principle 

 has any real physical basis or significance. To settle 

 this point, I undertook a careful survey of the figures 

 and carried out a series of computations with the aid 

 of my research student Mr. A. S. Ganesan, and have 

 come to the conclusion that the approximate agree- 

 ments between the calculated and actual frequencies 

 are merely fortuitous arithmetical coincidences. This 

 is clear from the following facts brought out by a 

 survey of the figures : 



(1) The proposed combination formula with its 

 freedom of choice of four numbers gives a very large 

 number of lines out of which it is possible to pick out 

 a few coinciding approximately with practicallv any 

 arbitrary series of frequencies which may be proposed, 

 the accuracy of fit increasing as the quantum numbers 

 chosen are increased. 



(2) The coincidences between the calculated and 

 observed frequencies are most numerous and accurate 

 precisely in the region where the density of either 

 series of frequencies is greatest, which is what we 

 should expect according to the laws of chance. 



(3) It is not, in general, possible to get a good fit 

 for the earlier members of a line-series except by 

 using large quantum numbers. This is what we 

 should expect if the coincidences were fortuitous, as 

 the frequency-differences between successive lines are 

 greatest in the beginning of a series. 



(4) More than one combination of quantum 

 numbers will fit a given line tolerably well. For 

 example, the D 3 line of helium is also represented 

 fairly well by I3-2I/5-I2. 



(5) The quantum numbers giving the best fit do 

 not fall into any regular sequence when arranged 

 either according to the frequencies of the lines or their 

 intensities, nor do they show any characteristic 

 differences for the singlet and doublet series. 



Needless to say, the foregoing remarks apply with 

 even greater force to the case of the lithium atom 

 when a choice of six numbers is permitted. 



Finally, it may be remarked that the Rydberg 

 constant 109723 chosen by Dr. Silberstein is appro- 

 priate only to the case of the ionised helium atom in 

 which only one electron is coupled to the nucleus. 

 If both electrons exert reactions on the nucleus and 

 move simultaneously, the value of the Rydberg 

 constant cannot remain the same in general. 



C. V. Raman. 



210 Bowbazaar Street, Calcutta, 

 October 18, 1922. 



Water Snails and Liver Flukes. 



Having been attracted on several occasions by 

 the presence of actively swimming cercariae of 

 Fasciola hepatica in material collected for protozoan 

 studies and searching for the intermediate host, 

 I have come across several examples of Limnaea 

 peregra harbouring perfectly developed cercariae of 

 the same species. Prof. Graham Kerr has also had 

 similar experiences. 



NO. 2769, VOL. I IO] 



May I claim the hospitality of your pages to ask 

 of your readers for references to literature dealing 

 with the subject of any intermediate host, other 

 than L. tvuncatitla, of the liver-rot parasite? Mr. 

 Staig has kindly informed me that Prof. J. W. W. 

 Stephens writes in " Animal Parasites of Man," by 

 Fantham, Stephens and Theobald: "In the allied 

 species of L. peregra the fluke will develop up to a 

 certain stage but never completes all its various 

 phases." Many text-books in zoology give one the 

 impression that L. truncatula is the only intermediate 

 host. 



My experience in searching for L. truncatula is 

 that the occurrence of the snail is very local in 

 S.W. Scotland. It seems to be rare, or altogether 

 absent in some districts. Yet in these districts the 

 sheep are known to be infected with the liver-rot 

 disease. It would seem, then, that /.. peregra acts as 

 the normal intermediate host in those districts, the 

 Fasciola completing within its body in normal fashion 

 the life cycle up to the stage when the cercaria 

 becomes free. Monica Taylor. 



Notre Dame, Dowanhill, Glasgow. 



A Mutation of the Columbine. 



Last summer a remarkable mutation of the blue 

 columbine (Aquilegia ctzrulea James) was discovered 

 by Miss Madeline Gunn near the Smuggler Mine, 

 in the vicinity of Ward, Colorado. Only a single 

 plant was found, growing under a spruce tree. The 

 flowers are of good size (about 63 mm. diameter), 

 with the pale blue sepals deeply trifid apically, the 

 divisions about 12 mm. long, broad basally, the 

 outer ones overlapping the median one (Fig. 1). In one 

 case the median division is bifid apically. The petals 

 are white, the laminas and spurs shorter than usual. 



Wuh -tnljidiaj. 

 half net-. J.-ie, 



The form may be called unit, trifida ; it represents 

 a striking new type which, if it can be propagated, 

 will be a notable addition to horticulture. Were it 

 received from some remote region, it would appear 

 to be a very distinct new species, or some might 

 even wish to separate it generically. The trifid 

 structure is characteristic of the divisions of the 

 leaves of Aquilegia, and no doubt we may say that 

 a quality of the leaf has been transferred to the 

 sepals. "Numerous cases of phyllody of the calyx 

 in various flowers have been described by Maxwell 

 Masters and others, but in this case the sepals are 

 not at all leaf-like, and if such flowers were common 

 they would not strike any one as abnormal. 



t. d. a. cockerell. 



Dorothy Young. 

 University of Colorado. 



Y 2 



