78 



NATURE 



{May 26, 1887 



that anyone should, in a text-book for students, "discard the 

 ophthalmic somite of their seniors, and press the telson into the 

 service," a procedure on which he comments thus -.—"The 

 introduction of so sweeping a change into a book for juniors, 

 without due comment is, under these circumstances, a false step, 

 especially when it is considered that the precise conver.=c is 

 stated in all other books current." 



Now Claus in his text-book says (I quote from the English 

 edition) :— " The facetted eyes are borne on two movably sepa- 

 rated stalks. These were for a long time considered as the 

 anterior pair of appendages, while in fact they are merely lateral 

 portions of the head which have become jointed " ; and else- 

 where : "The last abdominal segment, which is transformed 

 into a telson." 



Gegenbauer in his text-book says: — "The projecting cha- 

 racter of the eye, owing to its curvature, may lead to a stage in 

 which the eye is stalked. When still more developed, this stalk 

 may become movable " ; and nowhere speaks of the stalk as the 

 homologue of an appendage. 



Prof. Lankester's pupils are all taught to regard the telson as 

 a somite and the "ophthalmic somite" as an erroneom inter- 

 pretation of parts. 



I fail to see, therefore, that Prof. Marshall need offer any 

 excuse for his method of counting the segments, nor, in an 

 elementary text-book, discuss a question on both sides of which 

 there is avowedly much to be said. 



I may note with regard to one other criticism that, although 

 there is nothing "irrelevant or absolutely fantastic" about 

 the term commissure, it is convenient to distinguish between 

 "commissures connecting two ganglia of the same pair" and 

 "connectives connecting ganglia of dissimilar pairs " (" Encycl. 

 Brit.," ed. ix. Art. "Mjllusca"). The " word-mongerers " 

 are here marking " a turning-point in advance." 



Madras, April 20. A. G. Bourne. 



"On t'.ie Establishment of the Roman Dominion in 

 South-East Britain." 



In my article on the above subject printed in Nature, vol. 

 xxxv. p. 562, I have briefly alluded to the ridiculous mutiny of 

 the Roman soldiers. I ought to have added (from Dio) the rela- 

 tion of the following incident, which terminated the mutiny : — 



"Taking courage, because a brilliant meteor rising in the 

 east passed across to the west, to the part to which they were 

 making their course, they descended on the island." 



That is, the Romans descended from an easterly part of 

 Europe upon Britain. 



This agrees with the course which in my former letter I 

 assigned as most probable ; namely, that the Roaians sailed from 

 the mouth of the Scheldt to Southend. G. B. Airy. 



The White House, Greenwich, May 18. 



FLORA OF CHRISTMAS ISLAND. 

 "IT HE Hydrographer of the Admiralty has kindly for- 

 warded to Kew, as he has stated in his note in 

 Nature for May 5, p. 12, the botanical specimens 

 collected during the visit of H.M.S. Flying-Fish to 

 Christmas Island. They were unfortunately, as explained 

 by Capt. Maclear, a mere residue of the collection which 

 was obtained. The examination of a better preserved 

 and more extensive one would be interesting, as the flora 

 IS evidently of a less common-place kind than that gener- 

 ally met with in coral islands. 



In all, twenty-four species admitted of approximate 

 determination. Of these five were ferns, all widely-spread 

 species. Of the remaining nineteen flowering plants five 

 are also probably identical with widely-distributed species, 

 and they occur in the Cocos or Keeling Islands between 

 which and Java Christmas Island lies. The much more 



imited flora of these islands is only known from the col- 

 lections of the late Mr. Darwin, and of Mr. H. O. Forbes 

 Of the remaining fourteen species at least six must be 

 set aside, the specimens being too imperfect to be more 

 than approximately determinable. Of the rest, two, 

 ? "i'^'c "^v"" ^- ^^'^^^^' V^hl, and an Ehretia, may, 



in Prof. Ohvers opinion, possibly be new; the teak 



{Tectona grandis, L. f.) occurs generally in the Malayan 

 Archipelago ; Euphorbia Chamissonis is interesting as a 

 Polynesian type ; fruits of Barringtonia are thrown up 

 universally on shores in the Malayan waters ; Terminalia 

 Catappa, L., is found pretty well everywhere in the tropics ; 

 the remaining two suggest no special remark. 



The collection unfortunately throws httle light on the 

 composition of the dense arborescent vegetation with 

 which Capt. Maclear found it to be covered. Teak pro- 

 bably forms large trees. Cordia subcordata, Lam., which 

 occurs also in the Cocos-Keeling Islands, and, according 

 to Mr. H. O. Forbes, originally covered them abundantly,i 

 is known there as " iron-wood," and is no doubt one of 

 the iron-wood trees recognized by Capt. Maclear in 

 Christmas Island. It is widely distributed throughout the 

 Malayan Archipelago, and extends to the Philippines and 

 some of the Pacific islands.^ 



On the whole, it can hardly be doubted that Christmas 

 Island has been stocked with its flora by the agencies 

 described by Dr. Guppy, and worked out by Mr. W. B. 

 Hemsley in the " Botany Report of the Voyage of H.M.S. 

 Challenger" (vol. i. part 3, p. 310) : " Winds and currents 

 drift to their shores the fruits and seeds of the littoral trees 

 which ultimately form a belt, whilst the fruit-pigeons dis- 

 gorge the seeds or fruits of those often colossal trees 

 which occupy the interior.'' 



The former agencies brought no doubt Barringtonia, 

 Hibiscus tiliaceus, Terminalia, Cordia subcordata,Ochrosia 

 parviflora, and Pandanus. Carpophagous birds are else- 

 where known to bring a profusion of fruits of palms, nut- 

 megs, Euphorbiacece and Laicrinea^, and other arborescent 

 species. Upon this element in the flora of Christmas 

 Island the collection, as already remarked, throws insuf- 

 ficient hght. The flora of Java is still but imperfectly 

 known, and though there is no reason to believe that that 

 of Christmas Island contains any absolutely endemic 

 species, it would not be surprising if a careful examina- 

 tion yielded many plants new to science which have yet 

 to be ascertained from the larger contiguous island, from 

 which they have been derived. 



W. T. Thiselton Dyer. 



THE JOURNAL OF THE ROYAL MICRO- 

 SCOPICAL SOCIETY— RETROSPECTIVE 

 AND PROSPECTIVE. 

 'HP HE month of March 1878 will ever remain memor- 

 -*- able in the annals of microscopy in this country, 

 for it marked the regeneration of the Journal of the 

 Royal Microscopical Society, the most conspicuous feature 

 of which was the introduction, for the first time, of a 

 systematic record of current researches under the title 

 of " Notes and Memoranda." Now that the period of 

 editorship which vv^orked the change is fast approaching 

 its decade, we would wish to review the position, in antici- 

 pation of the introduction of still further modifications 

 which, it is to be assumed, the editors will adopt on 

 entering upon a second period. 



We read in the preface to the first volume that the 

 "Notes and Memoranda" are intended to present a 

 summary of what is doing throughout the world in all 

 branches of microscopical research. Whilst extracts from 

 English publications will not be excluded, preference will 

 be given to those of foreign countries, as being less easily 

 accessible. Amongst these will be included the Trans- 

 actions and Proceedings of the Academies of the United 



' '' Naturalist's Wanderings in the Eastern Archipelago," pp. 28.29. 



2 Mr. H. O. Forbes (I.e. pp. 26, 27) gives a curious account of the way in 

 which the labours of a crab turn the white calcareous fore-shore of coral 

 islands into "a dark vegetable mould." They do this by burying system- 

 atically particles of vegetable debris ; by scooping away the soil beneath 

 them they lower down even large branches of trees. The ground thus en- 

 riched is fitted for occupation by plants; and as Mr. Forbes particularly 

 noticed that they carry " down also the newly-fallen seeds of the iron- 

 wood " these industrious factors in the economy of a bare coral island not 

 merely prepare the soil but also plant it. 



