634 



NATURE 



[August 21, 19 13 



regions hepatiques, dans le prolongement des grandes 

 antennes, trois fortes epines plus developpees encore 

 chez l'adulte, et, a quelque distance en arriere, trois 

 epines branchiales anterieures qui semblent faire 

 defaut a ce dernier. Les grandes pointes marginales 

 des epimeres abdominaux ressemblent beaucoup a 

 celles de l'adulte, mais les petites n'existent pas encore, 

 les epines de la nageoire caudale sont moins nom- 

 breuses; toutes les autres, si abondantes chez l'adulte, 

 font completement defaut. D'ailleurs, les teguments 

 sont coriaces et sans calcification aucune, 1 'abdomen 

 est depourvu des sillons transverses qu'on observe chez 

 l'adulte, les pleopodes natatoires s'accouplent au moyen 

 de crochets retinaculaires, et les sternites thoraciques 

 se prolongent en une pointe a la base des pattes, 

 surtout a la base des pattes posterieures. 



Ainsi, le petit animal ressemble deja quelque peu a 

 une Langouste, mais il s'en distingue par de nom- 

 breux caracteres. On peut etre assure d'ailleurs qu'il 

 passe directement a la forme definitive, car les tres 

 jeunes Langoustes sont a peu pres de meme taille. 



On sait que la Langouste commune se range parmi 

 les Palinurides breVicornes (antennes internes a fouets 

 courts) ; il en est de meme de notre puerulus qui, par 

 la meme, ressemble aux puerulus de la Langouste du 

 Cap (Jasus lalandei), de la Langouste neo-zelandaise 

 ijasus verreanxi) et d'une espece caralbe, le Palinurus 

 longimanus. II se rapproche surtout du puerulus de 

 cette derniere espece, car il pr£sente comme lui des 

 pointes sternales et, comme lui egalement, un exopo- 

 dite flagelle sur les maxillipedes externes. Les pointes 

 sternales et le fouet des maxillipedes font totalement 

 defaut dans les autres puerulus brevicornes. 



Nous voici done, pour la premiere fois, completemeni 

 renseignis sur le ddvcloppemcnt post-embryonnaire 

 d'une espece de Langouste, et preeisement sur celui 

 qui nous inteYesse le plus, le developpement de notre 

 Langouste commune: j'en possede tous les stades, 

 depuis l'oeuf jusqu'a l'adulte" et notamment le pueru- 

 lus reste 1 jusqu'ici inconnu. Que devient ce puerulus? 

 II est, on le sait maintenant, d'abord p^Iagique a la 

 maniere des phyllosomes, mais il doit gagner tres 

 vite le fond ou il se cache et ou une mue lui fait 

 acqueVir la forme des Langoustes. 



Les r^sultats precedents semblent avoir quelque im- 

 portance, car ils donnent la solution definitive d'un 

 probleme qui occupait les zoologistes depuis pres d'un 

 siecle. Je dois en rendre graces au personnel si 

 nimablement devoue du Laboratoire de Plvmouth. sur- 

 tout au Directeur, M. Allen, qui fit multiplier pour 

 moi les pei hi 3 pelagiques, e1 :'i M. Clark, Assistant, 

 qui s'est emplove a rendre les occupations fructueuses 

 et, aided.- M. Gossen, a recueilli le premier exemplaire 

 de puerulus. J'adressc :\ tous mes vifs remerciments, 

 — et a vous aussi. Monsieur le Directeur, si, comme je 

 me olais a le croire, vous voulez bien donner I'hos- 

 pii _ .- 1 1 i t . '- de votre journal anglais a un travail effectu£ 

 par un Frangais dans les eaux anglaises. 



E. I.. Bouvier, 

 Professeur au Museum d'Histoire naturelle de Paris. 



The Laboratory, Citadel Hill, Plvmouth, 

 8 Aout. 



The Origin of Actinium. 



The question of the origin of actinium is one of 

 very great interest at the present time. The law 

 governing the position of the radio-elements in the 

 periodic table led A. S. Russell, K. Fajans, and myself 

 independently to predict the existence of a new mem- 

 ber of the uranium series, the direct product of 

 uranium-X, occupying the vacant place in the periodic 

 table in the VA family, the heaviest known representa- 

 tive of which is tantalum. I suggested that if this 



NO. 2 2 86, VOL. 91] 



" eka-tantalum " disintegrated dually, as in the case 

 of the C-members occupying the place in the VB 

 family, one mode with the expulsion of a /3 and the 

 other with the expulsion of an a ray, the product of 

 the first mode would be uranium-II., and of the second 

 actinium. This could only have remained undetected 

 if eka-tantalum had a very long period. The sugges- 

 tion was disproved almost at once by the discovery of 

 the missing element by Fajans and Beer, which has 

 since been confirmed by Hahn and Meitner, and also 

 by Fleck in this laboratory. It turns out to be a very 

 short-lived member with a period of average life of 

 about 1-7 minutes, and gives rays only, the hard 

 rays before ascribed to uranium-X, which itself gives 

 only soft /3 rays. 



The obvious alternative was that actinium must be 

 produced from radium in a (3-ray change, that is that 

 the first change of radium must be dual, the well- 

 known a-ray change into emanation taking place 

 simultaneously with a /3-ray change into actinium. 

 This suggestion receives some support from the fact 

 that radium, as found by Hahn and Meitner, does 

 give, in addition to a rays, a very soft /3 radiation. 



But some experiments, of which I now wish to 

 give a preliminary account, seem also to disprove 

 this alternative. A specimen of Giesel's original 

 radium bromide, now ten years old, containing 

 13-2 mgs. of radium (element) on the international 

 standard, has been examined for actinium, and not 

 the least trace could be detected. During the whole 

 time since it was purchased, it had not previously 

 been removed from its original ebonite capsule or sub- 

 jected to any treatment. It was found to consist for 

 the most part of insoluble sulphate, due to its action, 

 no doubt, upon the sulphur in the ebonite capsule. It 

 was brought into complete solution as chloride, 

 radium-D, -E, and -F removed with a trace of bismuth 

 by hydrogen sulphide, and a trace of aluminium 

 chloride added and removed with ammonia. The 

 aluminium hydroxide was repeatedly dissolved in acid 

 and reprecipitated with ammonia until free from 

 radium. The actinium and radio-actinium would re- 

 main with the aluminium, the actinium-X being com- 

 pletely removed with the radium from which it is non- 

 separable. Tests for the active deposit were carried 

 out in a stream of air, designed to replace the air in 

 the box containing the preparation once every 5-6 

 seconds, the period of the actinium emanation. This 

 was in order to suppress the effect of anv radium 

 relatively to that of the actinium, but it was not neces- 

 sary, as neither radium nor actinium were present. 

 On the other hand, a minute amount of the pure 

 thorium active deposit was detected. 



The a-ray effect obtained in the air stream men- 

 tioned with three hours' exposure, four days after 

 preparation, when one-half of the equilibrium amount 

 of thorium-X would be present, equalled that of about 

 0-15 mg. of uranium oxide, and was amply sufficient 

 to characterise beyond all doubt. At first sight this 

 result is surprising, but it is exactly what is to be 

 expected if the chemical operations had been success- 

 ful in their purpose. For there is thorium in 

 Joachimsthal pitchblende, withal a very minute 

 amount, and the corresponding mesothorium would 

 be quantitatively removed with the radium, in the 

 course of time to grow radiothorium. The detection 

 of this infinitesimal trace of radiothorium by the active 

 deposit test is a guarantee that if actinium had been 

 formed it would have been detected, for radio- 

 actinium and radiothorium are non-separable. An 

 actinium active deposit, equivalent to less than 

 o-i mg. of uranium in activity, could have been de- 

 tected, and, takinf into account the various correc- 

 tions, it is reasonable to conclude that the full equili- 





