NATURE 



\Sept. 14, 1 i 



meter column. You have only to imagine a sensitive plate 

 moving at a uniformly rapid rate taking the 1 lace of the screen, 

 and you have as the result the photograph (Fig. 10) which I show. 

 Here are the electrical effects of several successive excitations re- 

 corded by light with unerring exactitude. In each, the diphasic 

 character is distinct, and vou see that the first or negative ] hase 

 lasts less than a second, but that the positive, of which the extent is 

 much less, is so prolonged that before it has had time to subside 

 it is cut off by another excitation. 



It would have been gratifying to me, had it been possible, to 

 exhibit to you other interesting facts relating to the excita- 

 tory process in our leaf. It has, I trust, been made clear to 

 you that the mechanism of plant motion is entirely different 

 from that of animal motion. But obvious and well marked as 

 this difference is, it is nevertbele-s not essential, for it depends 

 not on ( ifference of quality between the fundamental chemical 

 processes of plant and animal protoplasm, but merely on dif- 

 ference of rate or intensity. Both in the plant and in the 

 animal, work springs out of the chemical Iran- formation of 

 material, but in the plant the process is relatively so slow that it 

 must necessarily store up energy, not in the form of chemical 

 compounds capable of producing work by their disintegration, 

 out in the mechanical tension of elastic membranes. The plant 

 cell uses its material continually in tightening springs which it 

 has the power of letting off at any required moment by virtue of 

 ihat wonderful property of excitability which we have been 

 studying this evening. Animal contractile protoplasm, and par- 

 ticularly that of muscle, does work only when required, and in 

 doing so, uses its material directly. That this difference, great 

 ;>s it is, is not essentia', we may learn further from the consi- 

 deration that in those slow motions of ihe growing parts of plants 

 which form the subject of Mr. Darwin's book, "On the Move- 

 ments of Plants," there is no such storage of energy in tension of 

 elastic membrane, there being plenty of time for the immediate 

 transformation of chemical into n echanical work. 



I have now concludsd all thai I have to say about the way in 

 which planis and animals respoi d to external influences. In 

 this evening's lecture \ou have seen exemi lifted the general fact, 

 applicable alike to the physiology of plant and anin.al, that 

 v hatever knowledge we possess has been gained by experiment. 

 In speaking of Mimosa, I might have entertained )0u with the 

 ingenious conjectures which were formed as to its mechanism at 

 a time when it was thought that we could arrive at knowledge 

 I y reasoning backwards — that is, by inferring from the struc- 

 ture ol living mechanism what its function is likely to 1 e. In 

 certain branches of physiology something has been learnt by 

 this plan, but as regards our present investigation, almost noth- 

 ing, nor indeed could anything have been learnt. Everywhere 

 we find that nature's means are adapted to her ends, and the 

 more perfectly, the better we know them. But, wilh rare 

 exceptions, knowdedge is got only by actually seeing her at work, 

 lor which purpo.-e, if, as constantly happens, she uses conceal- 

 ment, we must tear off the veil, as you have seen this evening, 

 by force. Have we ihe right to assume this aggressive attitude? 

 Ought we not rather to n aintain one of reverent contemplation — 

 waiting till the truth comes to us? 



I will not attempt to answer this question, for no thoughtful 

 person ever asked it in earnest. Ano'her question lies behind 

 it, which is a deeper and a much older one. Is it worth while? 

 Is the knowledge we seek worth having when we have got it? 

 Notwithstanding that so recently even those who are least con 

 versant with our work have been compelled to acknowledge the 

 beauty and completeness of a life devuted to biological studies, 

 still the question is pressed upon us every hour — How can you 

 think of spending days in striving to unravel the mechanism oi a 

 leaf, w hen you know all the time that if there were no such thing as 



I tionaea, the world w ould not be less virtuous or less happy ? That 

 is a question which I willingly leave to those who put it. From 

 their point of view it does not admit of an answer ; from mine 

 it does not require one. They must go on seeking for and find- 

 ing virtue and happiness after their fashion; we must go on 

 after ours, striving by patient continuance in earnest work, 



I I learn year by year some new truth of nature, or to under- 

 stand some old one better. In so doing, we believe that we 

 also have our reward. 



THE BRITISH ASSOCIATION 

 REPORTS 



Third Report of the Committee appointed jor the Purpose of 

 Reporting on Fossil Polyzoa (Jurassic Species— British Area 



only). Drawn up by Mr. Vine (Secretary). — A partial examina- 

 tion of the Jurassic Polyzoa was made by Goldfuss (Pethfacta 

 Get mania, 1S26-33), but the author is not aware whether he had 

 any English examples of the types described and figured by him. 

 With the exception of the Aulopora, all the types are foreign, 

 and he does not find any reference 10 British si ecies in his text. In 

 the " Geological Manual " of De la Beetle, published in 1832, a 

 list of species is given, but only two are named as found within 

 the British area— Cellipora orbiculata, Goldfuss ( — Berenicea, 

 Lamouroux), and Mi/lepoia straminea, Phill. In the "Geology 

 of York," ed. 1S35, Phillips gave three species only — M. 

 straminea, Cellarta Smithii [Hippothoa (?), Morris's Catalogue 1, 

 Scarborough, and an undescribed Retipora (?). When, in 1843, 

 Prof. Morris published his "Catalogue of British Fossils," iht-re 

 was a large increase of species, but many of these had not been 

 thoroughly worked. In 1S54, Jules Ilaiue examined critically 

 ihe whole of the Jura-sic Polyzoa then known, and many 

 English naturalists fmni-hed him with material from their own 

 cabinets so as to enable him to correlate British and foreign 

 types. Lann uroux, Defranc, Mi'ne Edwards, Michel n, Blain- 

 ville, and H'Orbigny have published descriptions of Jurassic 

 species, and a list of the e, so far as | ossible, will be given at 

 the end of this report. Prof. D. Braun, by the publication of 

 his 1 aper on species found in the neighbourhood of Metz, added 

 materially to our knowledge of French Jurassic types, and later 

 foreign authors, Dumortier Waagen and others, have increased 

 'he number of described specie-, .since ihe publication of 

 Haime's work, much valuable material has been accumulating 

 in the cabinets of collectors, and Mr. Vine willingly draw up a 

 monograph if desired to do so. In the meantime he offers, in the 

 following re 1 ort, a rather compact analysis of genera and species 

 known by name or otherwise to tbe palaeontologist. 



Classification. — Haime's arrangements of the Jurassic Polyzoa 

 is very simple ; all his species, excepting two, are pi ced in one 

 family, the Tnbiiliporidic. In the "Crag roljzoa," 1859, Prof. 

 Husk gave a synopsis of the " Cyclostomata," arranged in eight 

 family groups, which were made to include several Mesozoic 

 types. This arrangement, with a slight alteration, was followed 

 by Smilt, Busk to some extent accepting the modification for ihe 

 arrangement of recent Cyclostomata in his later work (" Brit. 

 Mus. Cat.,'" pt. iii., 1S75). 'Ihe Rev. Thomas Hincks ("Brit. 

 Marine Polyzoa," 1SS0) disallows the family arrangement of 

 Busk in -o far as it relates to British species. .The Tulntliporida-, 

 Hincks, include, in part, three of the families of Busk. In this 

 report Mr. Vine follows Hincks as far as he is able to do so, as 

 many of the Jurassic species may be included in the family 

 Titlmliporida as now de;cribed. It will, however, in the present 

 state of our knowledge at least, be impossible to arrange the 

 species stratigraphically, as many, having the same type of cell, 

 range from the Lias upw ards. As far as the author is able to do 

 so, he gives the range of the species, beginning, of course, with 

 the lowest si rata. 



Class Polvzoa. Sub-order Cyclostomata, Busk. Fam. I. 

 Crisida-, Busk. — No fossils belonging to this family are at pre- 

 sent known to have existed in the Jurassic epoch. 



Fam. 11. 18S0. Tubuliporidxc, Hincks. — Zoarium entirely 

 adherent, or mi re or less free and erect, multiform, often linear, 

 or flabellate, or lobate, sometimes cylindrical. Zoceeia tubular, 

 disposed in contiguous series or in single lines. Oacnim, an 

 inflation of ihe surface of the zoarium at certain points, or a 

 modified cell" (vol. i. p. 424). 



1S25. Slomalopo/a, Bronn. 1821. Alecto, Lamx. ; 1S26, Aulo- 

 pcra (pars), Goklf. — The Reporter has already done partial justice 

 to the umserial Slomatopora, found in the Palaeozoic rocks of this 

 and other countries. He has again studied the species described 

 by James Hall, Piof. Nicholson, and himself, and he cannot, at 

 present, detect any generic character in the species that may be 

 used by the systematic pa 1 aeontologist to separate the Palaeozoic 

 from the Mesozoic types. He mu t, therefore, regard the Stoma- 

 topora of the two epochs as one, though the sequence is broken 

 in the Pala-ozoic — no species having as yet, he believes, been 

 recorded from the Carboniferous series of this or any other 

 country. 



In our modern classification (Hincks) we have a sub-genus, 

 Proboscina, which links together the genera Slomatopora and 

 Tubulipora. 1 laime's second genus is a!-o called Proboscina, 

 but there seems to me to be a great difference between the recent 

 and fossil species. The type of the recent sub-genus Slomato- 

 pora incrassata, Smitt, is a very peculiar species as regards the 

 cells, and he knows of no Jurassic type that can compare with it. 



