304 



NATURE 



[January 27, 1898 



that it is not readily determined by direct measurement. The 

 uniformity of different portions of the film is shown by allow- 

 ing the stars to trail over the plate. A much more delicate 

 test was found in the discussion of a series of measures of the 

 variables discovered by Prof. Bailey in the cluster Messier 5. 

 Sixty-three of these variables were compared on 41 plates by 

 Argelander's method, with a sequence of comparison stars. 

 Estimates were made of the difference in grades of each variable 

 from the next brighter and the next fainter star of the sequence. 

 The sum of these differences gives the interval between the 

 comparison stars, and combining all the results gives, in general, 

 several measures of each interval on each plate. Each com- 

 parison star in turn may then be regarded as a variable, and 

 its changes in light determined from the next brighter and next 

 fainter star of the sequence. Comparatively few measures were 

 made of the six brightest and the three faintest stars of the 

 sequence. The five intermediate stars were measured on 41, 

 39. 38. 30 and 30 photographs respectively. On the average, 

 therefore, five stars were measured on 35 plates, which gave a 

 range of 0'I2 magnitudes and an average deviation of 0'02 

 magnitudes. The average deviation 0"02 includes: (i) the 

 errors of observation ; (2) errors due to neglecting hundredths 

 of a magnitude ; (3) errors due to irregularities in the film 

 which enter with their full value into the result. Since the 

 combined effect of these three sources of error is only + 0-02, 

 it is evident that neither of them can be large. The errors due 

 to the film are in fact so small, that there is no evidence that 

 they exist, and more delicate methods of measurements are 

 required to render them perceptible. 



THE COMPARATIVE PHYSIOLOGY OF THE 

 SUPRARENAL CAPSULES} 



p\R. SWALE VINCENT has in previous communications 

 ■^-"^ given certain experimental evidence in favour of the view 

 that the paired suprarenal bodies and the inter-renal gland of 

 Elasmobranch fishes correspond respectively to the medulla and 

 the cortex of the suprarenal capsules of the higher Vertebrata. 

 This evidence consisted in the utilisation of the discovery of 

 Oliver and Schafer that the medulla of mammalian suprarenal 

 contained a substance which, when injected into the circulation, 

 produced an enormous rise of blood-pressure. Dr. Vincent 

 ound that the paired bodies of Elasmobranchs contained this 

 active substance, while the inter-renal gland in the same order of 

 fishes and the known suprarenals of Teleosts did not. Thus it 

 appeared that the medullary portion of the suprarenal was 

 absent in Teleosts, the suprarenal bodies in this order of fishes 

 consisting solely of cortex. 



Since performing the above experiments his attention has 

 been given to the general physiological effects of extracts ob- 

 tained from suprarenal capsules. The extracts were made sepa- 

 rately from cortex and medulla, and injected subcutaneously 

 into various mammals. It was noted that the injection of 

 medullary material was invariably fatal if a sufficiently large 

 dose were administered, while the cortical extracts produced no 

 appreciable physiological effects. The mode of preparing the 

 extracts was usually by boiling for a short time in water or 

 normal saline, and carefully filtering, as it had been found that 

 boiling, if not too prolonged, did not destroy the active 

 material. The symptoms usually observed were a characteristic 

 progressive paralysis, with occasionally convulsions. Death 

 probably occurred by respiratory paralysis. 



Since these effects were only produced by medullary substance, 

 there appeared now to be afforded a still further means of testing 

 the above views concerning the homologies of the two kinds of 

 suprarenal in Elasmobranchs and the corpuscles of Stannius in 

 Teleosts with the two portions of the suprarenal capsules of the 

 higher Vertebrata. Accordingly, in the present communication 

 the hypothesis has been established on a still firmer basis by 

 testing the effects of the two kinds of gland in Elasmobranchs 

 and of the cortical suprarenals of Teleosts, where extracts of 

 them are injected subcutaneously into small mammals. Naturally 

 only very small quantities of material have been available for 

 this purpose, but the effects upon mice have been quite definite. 

 Material from Gadus morrhua produced no effects whatever. 

 The paired bodies from Scylliiim canicida and Raja clavata 



1 Abstract of a paper entitled "Further Observations upon the_ Com- 

 parative Physiology of the Suprarenal Capsules." By Dr. Swale Vincent. 

 (Read before the Royal Society, November 25, 1897. 



produced characteristic symptoms and a rapidly fatal result. 

 Again, the inter- renal from these genera was found to be inactive. 

 One of the mice certainly which was injected with an inter-renal 

 extract was found dead on the following day, but Dr. Vincent 

 thinks this result can reasonably be attributed to contamination • 

 with the paired bodies, and is analogous to the effect one some- 

 times obtains upon the blood-pressure when inter-renal extract 

 is injected intravenously. The symptoms noted in the mice as 

 the result of injection of the active material were quickened 

 respiration at first, which afterwards became slower and slower, 

 and paralysis commencing in the hind-limbs, and finally affect- 

 ing the whole body. In one case there were convulsions. In 

 fact, the results were typically those of poisoning by suprarenal 

 medulla. 



These experiments afiford further positive evidence of the 

 homology of the paired bodies of Elasmobranchs with the 

 medulla of the mammalian suprarenal. The direct evidence 

 in favour of the homology of the inter-renal with the cortex of 

 the suprarenal is mostly morphological and histological, and 

 this the author has detailed elsewhere. 



MIMICRY IN INSECTS} 



CHARING in the perplexity avowedly felt by many of my 

 *^ predecessors in this chair as to the choice of a subject for the 

 annual address — perplexity arising rather from the redundancy 

 than from the scarcity of entomological matter — I have been 

 led to think, considering the wide-reaching importance of the 

 questions involved and the unmistakeable interest shown in the 

 recent discussion at two of our meetings, that some account of 

 the mimetic relations existing among insects might not be out 

 of place. Having for a considerable period devoted some 

 attention to the matter, I propose to pass in review what has 

 been placed on record ; and if, in so doing, I traverse ground 

 very familiar to most of us, my excuse must be the fascinating 

 interest which attaches to the whole subject. 



Early Contributions to Mimicry. 

 The application by Henry Walter Bates, our lamented Presi- 

 dent, of the great principle of natural selection in elucidation of 

 the mimicries found among insects is too well known to require 

 any detailed repetition heie. It is sufficient to recall that, as 

 the result of many years' experience in tropical South America, 

 Bates established the facts that (l) among the abundant and 

 conspicuous butterfles of the groups Danainoe, Heliconiinje, 

 Acraeinae, and some Papilioninae were found very much rarer 

 mimicing forms, chiefly of the group Pierinse but partly belong- 

 ing to other groups and some even to the Heterocera, which, 

 departing very widely from the aspect of their respective allies, 

 imitated with more or less exactness the abundant species in 

 question ; (2) the numerous and showy Danainre, &c., although 

 of slow flight, did not appear to be molested by the usual insect- 

 ivorous foes ; and (3) the members of these unassailed tribes 

 possessed malodorous juices not found in the mimicking forms or 

 their aUies. From these data he argued that the explanation of 

 these extraordinary resemblances was to be found in the great 

 advantage it would be to species undefended by offensive secre- 

 tions, and therefore palatable and much hunted down, to find 

 escape in the disguise of species recognised and avoided as un- 

 palatable ; and traced the mimicries to the long-continued action 

 of natural selection, perpetually weeding out by insectivorous 

 agencies every occurring variation not in the direction of likeness 

 to the protected forms, but as perpetually preserving, and so 

 aiding the development by heredity of, every variation favour- 

 able to the attainment of the protective mimicry. 



This sagacious application of the Darwinian theory in solution 

 of one of the most difficult and baffling of the problems pre- 

 sented to zoologists, was of the greatest service and encourage- 

 ment to all students of evolution. I retain to-day the liveliest 

 recollection of the delight I experienced in the perusal of a copy 

 of Bates's memoir received from himself ; for his work was not 

 that of the mere cabinet systematist, but came with all the force 

 of face-to-face commune with the abounding life of the tropics. 



Before two years had passed, Bates's explanation of mimicry 

 was confirmed by his former companion in exploration, Alfred 

 Russel Wallace, who, working with equal devotion in the 



1 Abstract of the presidential address delivered before the Entomological 

 Society of London on January 19, by Mr. Roland Trimen, F.R.S. 



NO. 1474. VOL. 57] 



