July 14, 1904] 



NATURE 



261 



othcruise explain the irnrease in rate of the heart-beats 

 which they not infrequently met with in their experiments. 



(41 Knhydrina venom has apparently no direct action on 

 the vaso-motor centre. 



(51 The blood-pressure curve in Enhydrina poisoning; is 

 a remarkably steady one, provided that moderate doses of 

 venom are given and that care is taken to avoid the in- 

 jection of large volumes of fluid into the blood vessels. 

 This is due to the fact that the blood pressure is exposed 

 neither to the influence of the rival forces which act on 

 the heart so strongly in cobraism, nor to the direct vaso- 

 motor changes which characterise the action of certain 

 other venoms. 



(6) The respiratory mechanism is that which is chiefly 

 affected by Enhydrina venom. If large lethal doses are 

 employed respiration falls rapidly, and a considerable rise 

 of blood pressure, asphyxial in origin, may precede death. 

 The heart-beat then quickly slows, and blood pressure falls 

 with corresponding rapidity. 



Obviously, these are simply the phenomena of rapid 

 asphyxiation. If, however, smaller lethal doses of venom are 

 employed, no marked rise in blood pressure occurs. The 

 ordinary level is maintained until near the occurrence of 

 death ; the beat then slows, and the blood pressure falls. 

 Here we have an expression of gradual cardiac failure, 

 brought about by slowly progressive asphyxiation. The 

 absence in slow Enhydrina poisoning of the large asphyxial 

 rises of pressure which are so characteristic of the final 

 stages of cobra poisoning is readily explained by the fact 

 that Enhydrina venom has no direct constrictive action on 

 the walls of the arterioles, such as cobra venom possesses. 



(7) As to the part of the respiratory mechanism that is 

 affected by sea-snake venom, the rapidity with which re- 

 spiration is affected, both when venom is injected into 

 a vein and also when it is applied directly to the medulla 

 oblongata, leaves no room to doubt that the respiratory 

 centre is directly acted on by the venom. On the other 

 hand, some degree of motor nerve-end paresis is constantly 

 present in animals dying from the effects of subcutaneous 

 injections of this venom. The fact is emphasised that, in 

 experiments carried out by dropping venom on the exposed 

 medulla oblongata, animals w^ere not killed through the 

 respiratory centre with their motor nerve-ends still un- 

 damaged. In this respect. Enhydrina venom differs in its 

 action from cobra venom. It would therefore appear that, 

 in poisoning with Enhydrina venom, motor nerve-end 

 paresis plays a much greater part than it does in cobraism. 

 It is not difficult to suppose that a blurting of the motor 

 nerve-end mechanism, even though far from absolute, may 

 seriously add to the embarrassment of a centre which has 

 already been directly and gravely enfeebled. 



" On the Structure and Affinities of Palajodiscus and 

 .\gelacrinus." By \V. K. Spencer, B..A., F.G.S. Com- 

 municated by Prof. W. J. SoUas, F.R.S. 



The method employed was that devised by Prof. Sollas 

 (Phil, Trans., B, vol. cxcvi.). This method introduces a 

 new field of research to paleontologists, for an accurate 

 model of the internal parts of fossils may be made bv the 

 investigator. Specimens of the above genera were ground 

 by a special machine at uniform distances of i 40th mm., 

 and each successive surface photographed. From tracings 

 of the photographs obtained wax models were built. 



Palaeodiscus and .\gelacrinus were chosen for investi- 

 gation because many observers have claimed them as 

 possessing primitive and ancestral characters. 



Palaeodiscus is one of the oldest echinoids known, occur- 

 ing in the Lower Ludlow beds of Leintwardine. It is 

 shown to possess features which are only found in embrvonic 

 .echinoids of the present day. 



No interambulacral plates are present in the peristomial 

 region. The interambulacrum possesses only a single 

 initial plate proximally to the mouth. The vast majority 

 •of the plates of the interambulacrum are rhomboidal. The 

 outer surfaces of the pyramids are concave. Other 

 Palaeozoic echinoderms may possess these characters, as 

 shown by Jackson, but no other echinoid possesses so 

 many undoubtedly primitive characters. This makes the 

 important discovery of Prof. .Sollas (confirmed by the 

 author), that there are two series of plates in the 

 ambulacrum, much easier to understand. The outer series 



NO. 181 I. VOL. 70I 



was compared to the true echinoid ambulacrals, the 

 inner .series to the asteroid ambulacrals. PaUTodiscus would 

 then be placed at the base of the echinoid stem, and would 

 enable us to derive the echinoids from asteroid ancestors. 

 The asteroid series of plates of Paljeodiscus is represented in 

 other echinoids by the auricles which were shown by Lov^n 

 to have an independent origin and growth. It 'is note- 

 worthy that this comparison was instituted by Johannes 

 Miiller so long ago as 1853. 



.^gelacrinus is a member of the recently revived group 

 of the Edrioasteroidea. This group has been claimed as 

 ancestral to free moving echinoderms bv Neumayer, 

 Haeckel, and Bather. The genus Edrioaster, on which 

 most of the previous investigations have been conducted, 

 lends support to this suggestion, for it possesses a double 

 series of flooring plates to the ambulacral groove between 

 which are pores. It was therefore suggested that since the 

 Edrioasteroidea alone amongst Pelmatozoa possessed pores 

 through which the eleutherozoan ampullce could be pro- 

 truded, they were the pelmatozoic ancestors of the free 

 moving echinoderms. 



Agelacrinus is shown, however, to possess single flooring 

 plates, and no pores are present either through or between 

 these plates. The pores of Edrioaster, therefore, are not 

 so characteristic or important a feature of the Edrio- 

 asteroidea as the above authors would claim. 



In conclusion, it is pointed out that the Asteroidea are 

 the most primitive Eleutherozoa, and their structure is 

 much too simple to be derived directlv from anv known 

 pelmatozoan. 



June 16. — " On the Relation between the Spectra of Sun- 

 spots and Stars." By Sir Norman Lockyer, K.C.B., F.R.S. 



In a previous paper on the chemical classification of the 

 stars the author suggested the probability that, as the result 

 of further work, the " genera " then proposed might have 

 to be split up into " species." During more recent re- 

 searches the temperature classification was tested by com- 

 paring the relative intensities of the red and ultra-violet 

 ends of the spectra of stars, situated on various horizons 

 of the temperature curve, including Capella and .\rcturus, 

 which, according to the original general classification, 

 belong to the same type, viz. " .Arcturian. " It was found 

 that the spectrum of Capella extended on an average about 

 70 tenth-metres further into the ultra-violet than" that of 

 .Arcturus, whilst the red portion of the spectrum is certainly 

 stronger in the latter. That is to say, the general tempera- 

 ture of .'Irctiiriis is probabh apprcciabh lower than that of 

 Capella. 



The next step was to see if chemical change accompanied 

 this reduction of temperature, and if so, whether the change 

 was in any way related to the change from the photosphere 

 to the sun-spot spectrum. In comparing, for this purpose, 

 the spectra taken with the 6-inch Henry prismatic camera, 

 it was noticed that certain lines were relatively intensified 

 in passing from the spectrum of Capella to that of .Arcturus. 



Similar comparisons of the Fraunhoferic spectrum with 

 the spectra of Capella and .Arcturus respectively were next 

 made. This work led to the following conclusions: — (i) 

 That the line absorptions of Capella and the sun are 

 practically identical ; (2) that although, speaking generally, 

 the same lines occur in the spectra of the sun and ."Arcturus, 

 yet in the latter many lines are relatively more intense than 

 in the former. Moreover, in the great majority of such 

 cases the lines so intensified arc probably due to vanadium 

 and titanium. 



Now an analysis of the widened lines observed in sun- 

 spots since the year 1804 has shown that the elenu-nls 

 chiefly affected are also vanadium and titanium. 



Thus it will be seen that whilst the temperature classifi- 

 cation certainly places Arcturus on a lower temperature 

 level than Capella, and, therefore, the sun, the evidence 

 obtained from a study of the line absorptions of Arcturus 

 and of sun-spots indicates very clearly that the temperature 

 of the Arcturian absorbing atmosphere is about the same 

 as that of the sun-spot nuclei during the above-mentioned 

 period. This conclusion justifies the ideas formulated by 

 De la Rue, Stewart, and Lcewy that the spots are produced 

 by the downrush of cooler material. 



Reference is also made to Prof. Hale's suggestion that 

 beciiuse the lines which are widened in sun-spots appp;ir as 



