jVA TV re 



[April 13, 1899 



remarkable in themselves, but also, as disclosing apparently 

 ancestral characters, af the deepest interest in their bearing on 

 the phylogeny of the species concerned. The latter aspect of 

 these investigalions has been ably dealt with by Dr. F. A. Dixey, 

 who, in his published comments on Mr. .Merrifield's papers of 

 1S93 and 1S94,' points out that they seem to go far towards in- 

 dicating the possibility that a disturbance of natural temperature 

 conditions, whether in the direction of heat or cold, can produce 

 in a monomorphic species a tendency towards reversion, and 

 also notes the production by these experiments of ancestral 

 features in Vaut'ssa io^ I', polychloros^ and Grapta C.-albutu. 



Concurrently with Mr. Merrifield's later work appeared both 

 Dr. M. Standfuss's - and Prof. VVeismanns ^ important memoirs, 

 containing accounts of the series of temperature experiments 

 carried on by them respectively in the course of the last decade. 

 Standfuss's paper of 1894 deals with the effects of the warm and 

 cold treatment of the summer pupce of nine species of European 

 butterflies. None of these can be included among seasonally- 

 dimorphic species in Europe itself, but the author points out 

 that the effect of heat on the Zurich pup;x; of Papilio mmhaon 

 was to produce specimens perfectly resembling the .August form 

 of the species that is found in Syria. Other striking results as 

 given by the experimenter were the production of specimens 

 representing (a) Local forms, such as constantly occur in nature 

 in certain definite localities ; in Vanessa urtka', Pyrameis 

 (ardui, and to some extent in Papilio machaon and Vanessa 

 iintiopa : {/>) Aberrations, like those which now occur in nature ; 

 in V. io, P. cardiii, and Argynnis aglaia : (c) Phylogenetic 

 forms, " which may have either existed in past epochs, or may 

 perhaps be destined to ari.se in future" t in certain cooled V. io 

 and J^. anliopa and certain warmed V. ala/anta, and the reverse 

 respectively. Noting the remarkable circumstance that the same 

 conditions lead to such diverse effects in different species— the 

 changes wrought in one species being entirely within the limits 

 of its variation at the present day, while in another they far .sur- 

 pass those limits — he suggests that thesi'ecies coming under the 

 former category are the phylugenetically older, and those belong- 

 ing to the latter are the phylogenetically younger. The author 

 found that the high temperature of 104' F. rapidly caused death 

 in nearly all the species tested—/', machaon and G. C. -album 

 proving least sensitive — but low temperatures prolonged for 

 even four weeks are much better tolerated ; and it was thought 

 that this favoured the conclusion that the species so tested " were 

 constrained in past ages to accommodate themselves much more 

 10 lower than to higher temperatures." 



In the edition of his " liandbuch," which appeared in 1896, 

 Standfuss recapitulated the cases published in 1894, and added 

 mention of a warmth experiment with Gonepteryx ihanini \\^\c\\ 

 had the effect of inducing in the females some indications of the 

 yellow colouring of the males. lie also gave excellent coloured 

 figures of most of the more marked variations resulting from 

 temperature treatment, some of them exhibiting marvellous 

 divergence from the normal form now existing in nature. 



Before turning to Weismann's memoir of 1895, it will be 

 convenient to refer briefly to Standfuss's recent and elaborate 

 treatise issued during 189S.' After reviewing (in Sect. I.) 

 his experiments as to effects from treatment of pupje with 

 constant moderately high (-^ J?' to 4-39' C. ) or moderately 

 low (-1-4° to -1-6' C.) temperatures in the years from 1S85 

 to the beginning of 1895, the author proceeds (in .Sect. II.) 

 to give an account of the continuation of these "Warm 

 and Cold " experiments during the succeeding period from 

 the middle of 1895 10 1897. These additional experiments 

 were made on no fewer than fifty-six species of European Lepi- 

 doptera (thirty-six butterflies and twenty moths), and on a 

 largely-increased number of specimens ; and their results were 

 found to be fully confirmatory of those derived from the earlier 

 more restricted experiments, affording various fresh instances 

 of the production of more or less marked variation in the 



< See Dr. DixcyV napcrs 0) " On Ilic Phyloi!cni-tic Significance of ihc 

 Variations produced l>y difTcrence of Temperature in Vanessa alalanta" 

 (.Trnm. KhI. Sm L.<n,l., 1893, p. 69): .ind l>) " Mr Merrifields Experi- 

 ments in Temperature Variation a.* Itearing on Theories of Hcredily." 

 (Of. cit., r8<34, p. 43Q.) 



* " L'efier die Grundc dcr V.irialiun und Alierration des Falterstadiums 

 bei den Schmetterjingen," 1894 (Kngl. tran^l. by Dr. V. A. Dixey in 

 £,iloiti,}ht-isl, 1895.) "Handbuch der PaL.'iiirkli»chen C.ross.Schmetter- 

 linge fur Forsclier und Sanimler," 1896. 



■' " Nt-w K\i)eriments on Ihc He.i>ona! nimorphism of [.epidoptera " 

 i8<)5). Km:!, ir.insl. I.y W. E. Nicholson in linlomalofisl. 1896. 



* '• K\pcritueiitcllc2ooloBi«cheSiudienmit Lepidopiern. A. Teinperalur- 

 Experimenle. ■ (PsHkichr. Schtveiz. X.iliirf-GeSMclUch.^ xxxvi. i. i8fl8.) 



NO. 1537, VOL. 59] 



directions previously indicated, viz. seasonal forms, local forms, 

 aberrations, phylogenetic forms, and forms showing assumption 

 of the male colouring by the female. Under the respective 

 headings of "Frost-Experiments" (Sect. III.) and " Heat- 

 Experiments" (Sect. IV.), the several results are given of em- 

 ploying temperatures under o°C. (0° to -l8°C., and excep- 

 tionally to — 20°C.), and those above -f 40° C. (up to -(- 45 C.) ; 

 and the attempt is made (.Sect. V.) to explain from the results 

 of these two sets of experiments the active cause of most of the 

 "Aberrations" occurring in nature. Attention is directed to 

 the extremely interesting fact that the aberrations resulting from 

 the artificial very high temperatures agree closely with the aber- 

 rations found in nature,' while aberrations like those produced 

 by the use of very low temperatures are never found in nature : 

 and the inference drawn from this is that the typical aberrations 

 occurring naturally among the Nymphlid.e are produced by the 

 temporary influence on a high degree of heat (40' to 45° C). 



I cannot here dci more than just refer to the remaining sec- 

 tions of Dr. Standfuss's treatise ; they include a consideration 

 of the mode of action of the frost and heat experiments, a discus- 

 sion as to the nature of aberrations, and an account of the further 

 breeding of aberrational Vanessa iirliiae, and with the conclud- 

 ing remarks at pp. 37 and 38 will well repay perusal. Some 

 idea of the satisfactory and extensive scale upon which the 

 experiments were conducted, may be gathered from Standfuss's 

 statement that he had employed altogether during 1S95-97 the 

 number of over 42,000 pupa; belonging to about sixty different 

 species." 



Weismann's memoir of 1895, above referred to, contains a 

 full record of his later experiments and results in the cases of 

 Arasihnia levaiia, Chrysophanus phlaeas, and Pienis napi, as 

 well as in those of Pararge egeria (with its "climatic variety," 

 nieione) and Vanessa uriieae. It further treats of the effect on 

 pup^ of variously-coloured light, and on hibernating pupa: of 

 warmth, and concludes with a comprehensive general review of 

 the whole subject, including a comparison of the results of some 

 of his own experiments with those obtained by Merrifield and 

 Standfuss. In the case of A, levana, he not only succeeded, by 

 means of temperatures of 27-28° C. and 30-32" C. , in obtaining 

 repeatedly a small number of the prorsa-ioxm from the second 

 summer generation of that form, but also proved that occasion- 

 ally the same result arose in isolated instances without the use 

 of a higher temperature than that of an ordinary warm room. 

 It was further established that the intermediate forms known 

 as poriina, so rare under natural conditions, are produced when- 

 ever a brood is subjected to an unsuitable temperature at the 

 beginning of the pupal stage, occurring indeed with the second 

 brood from unusual cold, and with the third brood from unusual 

 heat. As regards the seasonal forms of Pieris napi, it was 

 shown that the low temperature effects the conversion of the 

 summer form into the winter, only when specially applied 

 immediately after pupation ; while repeated experiments 

 with the variety biyoniae gave no suflicient supjmrt to Weis- 

 mann's view that this variety was the original parent-form 

 of napi. 



It is in this memoir that Weismann first recognises fully what 

 he had formerly que.stioned, but had latterly ("Aeussere 

 Einfliisse als Knlwickelungsreize," 1S94), put forward as 

 probable, viz. that, bcsitles the direct seasonal dimorphism 

 attributable to temperature, there also exists adaptiie seasonal 

 dimorphism dependent on the indirect influence of the varying 

 environment .according to the time of year. He again cites the 

 case of.-/, levana itself as possibly exhibiting in its//w.«2-form 

 mimicry of Limcnitis, and suggests that the seasonal fornis of 

 P. napi may be ailapted on the undersiilc to the vegetation 

 tints of spring and summer respectively. In the case of the 

 latter species he expresses the belief that .adaptive and direct 

 season.al dimorphism are ctimbined, pointing out that the 

 differences presented by the upperside may perhaps be referred 

 to the direct influence of temperature. The pos,sible adaptation 



J This is well itiustratcd by Plate IV. accompanying the memoir, where 

 figures of Aberrations. (.;) captured at large, and {ih forced at very high 

 temperature, of the following .species, are given side by side, viz. i'amessa 

 /vlycMoros, !■'. .i«//r./,i, P. alnlnHla, and i'yntmeit carxlni. Figs. 

 », 3, 5. 7 differing very slightly res[K:ctively from Figs. 2, 4, 6, and 3. 

 (Plate III. figures ihc .Aberrations proiluced in the same four specie s by 

 " Frost-Experiments ' ) 



- Dr. E. Fischer, of Zvirich, has also carried out very cxtensi\x tem- 

 perature experiments ori l^uropean l.epidoplera with most striking results, 

 which arc rnenlioni-,1 \.\ Weismann, Merrifield, and Standfuss. 1 ha\e not 

 seen Dr. Fischer's pubfishrd accounts of his work, but 1 believe he did not 

 experiment with .seasonally dimorphic species. 



