August 30, 1894] 



NA TURE 



435 



Kny on the correlation between root and shoot, ani an exhi- 

 bition of diagrams ; and by Prof. Pfeffer on the sensitiveness of 

 the root-tip. 



On Monday forenoon a series of papers dealing with various 

 points in the theory of evolution was taken before the Zoo- 

 logical Department. After the report of the Committee on 

 Telegony, Prof. D'Arcy Thompson read a paper on some 

 difficulties of Darwinism. He doubts the efficacy of the 

 struggle for existence in the case of humming-birds, &c., and 

 in these cases he regards the profusion of forms, colours, and 

 other modific.itions as due merely to laws of growth, and thinks 

 that growth may be more exuberant in the absence of struggle 

 and hardship. In other cases which are usually interpreted as 

 the result of natural selection, Prof. Thompson gave another 

 explanation, e.g. he considers the form of the Guillemot's egg 

 is merely the natural result of the pressure caused by a rela- 

 tively large egg passing dorvn a narrow muscular passage. 



Then Prof. C. V. Riley followed, on social insects and 

 evolution. He gave a summary of what is known of the 

 habits and economies of bees, wasps, ants, and termites, 

 especially as to the development of the young. He considered 

 that the varied structures and habits of neuters are perfectly 

 explicable upon the general principles which have governed the 

 modification of organisms, amongst which he believes natural 

 selection plays an important but limited part. He showed that 

 the differences between the queen and the neuter resulted en- 

 tirely from the treatment of the larva, and was at the control of 

 the colony. In ants also the differences between the different 

 individuals is again the result of food and nurture. He believed 

 with Darwin that the variations in social insects have been 

 guided by natural selection amongst colonies ; but that this re- 

 markable and somewhat unexpected social selection among 

 individuals, as exemplified in these insects, simplified the origin 

 of neuters. Competition had been between colonies rather 

 than individuals. The author finally pointed out that just as in 

 man among mammals, the higher intellectual development and 

 social organisation is found correlated with the longest period 

 of dependent infancy. 



Prof. Haycraft read a paper on the role of sex in evolu- 

 tion, in which he argued that variation is a quality of proto- 

 plasm, and that it has and can acquire this quality in varying 

 degree and apart from sexual conjugation ; also that sexual con- 

 jugation tends to limit or diminish variations, and that 'his is 

 the role of sex in evolution ; to sex therefore we owe our fairly 

 well-defined generic and specific groups. 



Dr. F. A. Dixey, in a paper on the relation of mimetic 

 characters to the original form, gave some interesting examples 

 of mimicry amongst butterflies, and showed how a very perfect 

 scheme of mimicry may be established by gradual changes 

 from a very small initial resemblance. 



Prof. Osborn treated of certain principles of progressively 

 adaptive variations observed in fossil series. He appealed for 

 a systematic analysis and investigation of variation, and for a 

 suspension of judgment in regard to the factors of evolution. 

 Recent works show a lack of analysis, since all adult variations 

 are classed together without regard to the two following 

 lines of cleavage ; first, as to adaptation, whether progressive, 

 retrogressive, or neutral ; second, as to time of origin in the in- 

 dividual, whether paIa;ogenic or neogenic. Neogenic variations 

 which point to the future may be conveniently divided into (a) 

 gonagenic ; {b) gamogenic ; (< ) embryogenic ; and (./) somato- 

 genic according to lines suggested by the work of Kolliker, 

 Weismann, Roux, and others. All previous inductions as to 

 variation have failed to recognise that the adult may exhibit 

 variations which have their immediate causes in all these periods, 

 although all alike spring from the potentiality of the germ. A 

 distinct consideration rises whether, besides the "minute varia- 

 tions "of Darwin and the "saltatory variations" of Hateson, 

 there may not be variations so slight as only to be measurable 

 by the comparison between two individuals separated by a long 

 genetic series. Evidence for variation of this kind is seen in 

 the contrast between the evolution of the premolars and of the 

 molars in the eocene horse series. The limitation of variation 

 to certain lines is seen in a comparison between the horse and 

 rhinoceros molars of the miocene. The general conclusion drawn 

 from these facts is that the pure selection principle is contra- 

 dicted by them, and there is some unknown principle of teleo- 

 logical mechanics yet to be discovered. 



In the discussion which followed, Prof. Poulton criticised 

 Osborn's classification of variations, and argued in favour of 



NO. 1296, VOL, 50] 



the action of natural selection in picking out the minute cha- 

 racters which distinguish individuals and in building them up into 

 varieties. The discussion was continued by Profs. Mivart, 

 Lankester, Seeley, Hartog, and others. 



In a paper on the wing of Archcsoptery.x viewed in the 

 light of that of some modern birds, Mr. \V. P. Pycraft showed 

 that in the development of the primary wing-feathers, as well 

 as in the general form of the manus, in the nestling of certain 

 gallinaceous birds there was evidence that they had descended 

 from a strictly arboreal form in which the manus of the nestling 

 was armed with claws to assist it in climbing the trees in which it 

 was reared, just as is the case in the young of Opisthocoimis 

 cristatus to-day. He showed that there is reason to believe 

 that the claws of Archaoptery.x were of prime importance only 

 during the nestling period of life. .V model of a restoration of 

 the wing of Archaopteryx was exhibited, in which it was demon- 

 strated that the remiges rested upon the third digit, the bases 

 abutting against that of the second digit, the top of which was 

 free. It was, however, suggested that this digit supported the 

 semiplume-like feathers seen in the fossil which possibly 

 functioned as coverts. 



In the Botanical Department : — On the origin of the sexual 

 organs of the Pteridophytes, by Prof. Douglas H. Campbell. 

 Notwithstanding the radical differences, especially in the 

 Archegonium, between the Bryophytes and the Pteridophytes, a 

 comparison of the structure and development of the sexual 

 organs of the higher Hepatics with those of the Eusporangiate 

 Pteridophytes shows poinis of resemblance enough to warrant 

 the hypothesis that here is to be sought the connection between 

 the Bryophytes and the Pteridophytes. Notes upon the ger- 

 mination of the spores of the Ophioglossese, by Prof. Douglas 

 H. Campbell. The author succeeded in germinating two 

 species, Ophioglossum pendulum and Botrychhim virginicum. 

 In both the first division of the spore occurs before any chloro- 

 phyll is formed. On sterilisation and a theory of the strobilus, by 

 Prof. F. O. Bo.ver. The following are some of the leading 

 points in Prof. Bower's theory : — The spore-bearing parts of the 

 sporophyte are to be regarded as primary in the evolutionary 

 history and in function. The homosporous vascular cryptogams 

 attained the climax of numerical spore production. As a con- 

 sequence of increased spore-production arose sterilisation of 

 sporogenous tissue in form of septa partitioning off loculi, and 

 subsequently the formation of synangia, and separation of the 

 sporangia. The sporogonial head is the correlative of the 

 strobilus or flower, the latter has eruptions of the surface to form 

 sporophylls upon which sporangia are borne. The evolutionary 

 history of the sporophylls shows progress from small and simple 

 to large and complex forms. Foliage leaves may have been 

 derived from sterilisation of sporophylls. The following are 

 the remaining papers brought before the Botanical Depart- 

 ment : — Miss N. Layard, a method of taking casts of the inteiior 

 of flowers ; Prof. E. Zacharias, the function of the nucleus ; 

 Prof. Errera, exhibition of diagrams ; Mr. G. Murray, on 

 Pachytheca ; Dr. Scott, the structure of fossil plants in its 

 bearing on modern botanical questions ; Prof. Marshall Ward, 

 a Thames bacillus ; Prof. Green, influence of light on diastase ; 

 and Mr. Seward, a contribution to the geological history o f 

 Cycads. 



The following are the remaining papers and exhibitions 

 brought before the Zoological Section ; most of them were taken 

 on Tuesday : — 



Dr. W. B. Benham expounded a new classification of the 

 Polychseta, which gave rise to some discussion. Prof. Jeffrey 

 Bell exhibited lantern slides of some magnificent colonies of 

 reef-building corals lately acquired by the British Museum. 



Dr. VV. B. Benham, on the blood of Magdona. It differs 

 from that of any other Cha;topod hitherto examined. Instead 

 of a red (haemoglobin) liquid plasma in which float either a few 

 nucleated colourless corpuscles or free nuclei, the blood-vessels 

 of Mageloiia are completely filled with very small spherical 

 globules of a madder pink colour, in an extremely small 

 amount of colourless plasma. These coloured globules are not 

 cells. There are free nuclei scattered amongst them, but the 

 coloured globules are not nucleated. The colour is due to a 

 pigment similar to ha^merythrin occurring in some Sipunculids. 

 The globules exhibit a very marked tendency to run together 

 like oil-drops and fuse. This viscid mass seems to be inter- 

 mediate between the absolutely liquid coloured plasma of 

 chxtopods and the red corpuscles of mammals which float in a 

 small amount of colourless plasma. Further, these globules in 



