446 



NA TURE 



[Fi 



AUV lO, 1910 



view, for if we accept it we must admit that the germ- 

 layers in arthropods and vertebrates are not homologous — 

 that the epi blast of the one becomes the hypoblast of the 

 other, and vice versa. Dr. Gaskell does not find this 

 difficulty by any means insuperable, and, as part of his 

 argument, runs a tilt against the germ-layer theory as at 

 present accepted. • In this he was largely supported by the 

 subsequent observations of Dr. Gadow and Prof. Stanley 

 Gardiner. 



The debate naturally centred around Dr. Gaskell 's 

 theory, which was discussed from the standpoints of 

 embryology, comparative anatomy, palaeontology, physio- 

 logy, and even psychology, the subsequent speaKers being 

 Prof. MacBride, Prof. Starling, Mr. Goodrich, Dr. Gadow, 

 Dr. Smith Woodward, Prof. Dendy, Sir Ray Lankester, 

 Dr. Chalmers Mitchell, Prof. Stanley Gai'diner, the Rev. 

 T. R. R. Stebbing, and the president tDr. D. H. Scott). 

 Dr. Gaskell replied at length at the end of the second 

 evening. 



It is impossible in this article to give more than a very 

 general account of the course of the discussion, and this 

 is the less necessary as the Linnean Society has announced 

 its intention of publishing it in full, while Dr. Gaskell's 

 views have recently been given to the world in book form. 



For reasons which have already been indicated, no 

 definite theory was put forward as a rival to that of Dr. 

 Gaskell, though probably no competent zoologist would 

 have much difficulty in formulating such a theory. 

 .'Xmphioxus, however, loomed large, especially in the re- 

 marks of Mr. Goodrich. Dr. Gadow, whose remarks, on 

 the whole, tended strongly to support Dr. Gaskell, ex- 

 pressed the opinion that the attempts which have been 

 made to bring Amphioxus into line have not been successful, 

 but it was pointed out that this animal, though in some 

 respects undoubtedly modified — according to Sir Ray 

 Lankester, even degenerate — nevertheless more nearly 

 resembles a primitive vertebrate than any other animal 

 living at the present day. Probably no zoologist now 

 claims it as being in the direct line of descent of the 

 higher vertebrates from their invertebrate ancestors, but 

 it has gone off on its own little side-track for only a 

 short distance from the starting point. In many respect;: 

 it retains primitive vertebrate characters, such as the noto- 

 chord, the numerous gill slits, and the comparativeh 

 undifferentiated central nervous system (which may, how- 

 ever, be partly explained as due to degeneration). It 

 shows hardly any sign of cephalisation, and no trace ot 

 the paired sense organs which form so dominant a feature 

 of the organisation in higher vertebrates. It represents 

 an altogether lower grade of organisation than the lamprey 

 or even the .\mmocoetes larva, yet, as Dr. Goodrich clearlv 

 showed, there is no difficulty in deriving the lamprey from 

 an Amphioxus-like ancestor by a normal process of evolu- 

 tion in which cephalisation has played the leading part. 

 If, however, we accept an Amphioxus-like ancestor as the 

 starting point of the vertebrate phylum, we must put the 

 arthropod theorv out of court at once, for many of the 

 structures upon which Dr. Gaskell lays much stress as 

 evidence in support of his theory, such as the lateral and 

 pineal eyes, have not yet appeared at the commencement 

 of the vertebrate series, and must have been evolved within 

 the limits of the phylum. 



As to what preceded the .'\mphioxus-like ancestor of 

 vertebrates, zoologists, as already observed, refuse to 

 commit themselves to an opinion. They await more 

 evidence. In the meantime, it is pointed out that the 

 possession of nephridia with solenocytes, identical with 

 those of certain ch.netopod worms, suggests annelidan 

 affinities, and that the worm-like Balanoglossus, with its 

 Amphioxus-like gill slits but very dubious notochord, must 

 also be taken into account, while the evidence of embryo- 

 'og.V points to some far remote relationship between 

 .Amphioxus, Balanoglossus, and the echinoderms. 



The chief difficulty in the way of comparing the verte- 

 brate with the annelid lies, of course, in the reversal of 

 the surfaces which such comparison implies. In the 

 annelid the principal part of the central nervous system 

 lies ventrally beneath the gut, in the vertebrate it lies 

 dorsally above the gut. Dr. Gaskell maintains that the 

 old w,ay of getting over this difficulty by turning the 

 animal upside down and making the dorsal surface of the 

 vertebrate represent the ventral surface of the invertebrate 

 NO. 2102, VOL.- 82] 



ancestor is now universally discredited. Yet we find Prof. 

 Sedgwick saying in his " Te.Kt-book of Zoology," so 

 recently as 1905, that it . quite clear that the dorsal 

 surface of the vertebrate corresponds to the ventral surface 

 of other coelomates, a view which is strongly supported by 

 the history of the ascidian tadpole, in which the mouth 

 is dorsally situated,' instead of ventrally, as in higher 

 chordates. 



A considerable amount of detailed criticism of Dr. 

 Gaskell's theory was, of course, brought forward during 

 the discussion. Prof. MacBride pointed out that the skin 

 of the primitive vertebrate must have been ciliated, while 

 in the arthropod the entire organisation is dominated by 

 the production of a thick, chitinous cuticle. He' also spoke 

 in defence of the germ-layer theory, and criticised Dr. 

 Gaskell's explanation of the hollow gastrula stage of the 

 arthropod Lucifer, the existence of which seems clearly to 

 indicate that the two primary layers of arthropods are 

 identical with those of vertebrates. 



.\n attempt was also made by the present writer to show 

 that Dr. Gaskell's interpretation of the lateral and pineal 

 eyes of vertebrates as the homologues of the lateral and 

 median eyes of arthropods would not bear the test of 

 critical examination. The same speaker endeavoured to 

 explain the hollow tubular character of . the vertebrate 

 central nervous S3'stem as a comparatively recent adaptation 

 to the requirements of the vertebrate organisation, in which 

 the necessary increase of surface is brought about by the 

 familiar process of folding. Dr. Chalmers Mitchell directed 

 attention to the mode of origin of the nervous system in 

 various invertebrate groups, and scored a point against Dr. 

 Gaskell by his reference to the recent conclusions of Prof. C. 

 Judson Hcrrick with regard to the arthropodan nervous 

 system. 



Prof. Starling maintained that, as regards the principles 

 which must guide any research into the phylogeny of our 

 race, a physiologist has as good a right to be heard as a 

 comparative anatomist, and he thinks that "it is as 

 difficult to conceive that the vertebrate was evolved from 

 a primitive worm-like organism which shot up past the 

 more highly developed .Arthropoda as it is to believe that 

 mankind is destined to be replaced by some beast that is 

 now being evolved from lower groups in the depths of 

 the sea." The observations of Dr. Smith Woodward, on 

 the other hand, which dealt with the subject from the 

 palsBontological point of view, seemed to indicate that the 

 process of evolution takes place very much in the way 

 which Prof. Starling finds it so difficult to imagine. More- 

 over, the claims of the ancient ostracoderms to arthro- 

 podan affinities, upon which Dr. Gaskell lays so much 

 stress, seem to be extremely dubious ; they were probably 

 highly specialised forms, perhaps related in some respects 

 to the lampreys. 



Though unable to accept his views on the subject before 

 the ineeting. Sir Rav- Lankester voiced what must have 

 been a very general feeling amongst those present in 

 expressing his appreciation of Dr. Gaskell's observations. 



Arthur Den'dy. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — The Vice-Chancellor gives notice that the 

 Sadlerian professorship of pure mathematics is vacant. 

 The election to the professorship will take place on 

 Monday, February 28. Candidates are requested to send 

 their names to the Vice-Chancellor on or before Saturday, 

 February 19. 



The office of superintendent of the museum of zoolog\' 

 is vacant by the resignation of Prof. Punnett. The stipend 

 at present attached to the office is 200!. per annum. 

 .Applications should be sent to the chairman of the special 

 board for biology and geology (Prof. Langley, The 

 Museums, Cambridge) on or before March 7. 



Mr. J. C. F. Fryer has been elected to the Balfour 

 studentship from March 25. 



.\ grant of 200/. has been made from the Balfour fund 

 to Mr. C. F. Cooper, for an investigation into the Tertiary 

 vertebrate fauna of India, and a grant of 40/. to Mr. K. R. 

 Lcwin, in furtherance of his work in protozoology to be 

 carried on abro.ad. 



The following grants were made in the year 1909 from 



