April 24, 1902] 



NA TURE 



5S5 



deplorable. There was no provision for either carrying on the 

 education of the best boys at the primary schools, or for educat- 

 ing the large class of sons of artisans and others for whom the 

 primary schools were insufficient and such private-adventure 

 schools as existed altogether inadequate. As a governor of the 

 Richmond School I am able to speak with confidence of the 

 remarkable success which has attended its establishment. 



As regards Surrey I do not see, therefore, that the Bill will 

 put us in a much better position than we are at present. But 

 the present crying need is that primary education should be 

 dealt with on the same lines. It would, in my opinion, be a real 

 disaster if the part of the Bill relating to it were to be dropped, 

 as has been proposed in these pages. 



In the Borough of Richmond the arrangements for primary 

 education can hardly be described as other than chaotic. I am 

 by no means persuaded that the establishment of a School Board 

 would make matters much better. We might gain something 

 in one direction at the cost of losing all chance of coordinating 

 our arrangements for primary with those for secondary instruc- 

 tion. The one should dovetail into the other, which it is 

 little likely to do if they are in dift'erent hands. I am wholly at 

 a loss to see why an organisation which has solved one problem 

 should not be able to solve both. 



Kew, April 21. W. T. Thiselton-Dver. 



The Dangers of Coral Reefs to Navigation. 



In consequence of a paper which I recently read before the 

 Royal Geographical Society on " The Formation of the Mal- 

 dives," I have received several letters from officers of the mer- 

 cantile marine. These lead me to believe that the danger 

 incurred by too closely approaching coral reefs and islands is not 

 generally perceived. Further, I have myself seen large passenger 

 steamers coasting round the south of Minikoi .Atoll within 

 300 yards of its encircling reef. Indeed, one large liner was so 

 close in that the look-out man at the mast head could not have 

 failed to see the bottom. The practice of approaching so near 

 where unnecessary — to enable passengers to get a good view of 

 the land and reef — is one attended with considerable danger and 

 greatly to be deplored. 



It is generally known that most reefs on their seaward faces 

 slope gradually from their edges to 25-50 fathoms, and then 

 more steeply to 100-200 fathoms. The breadth of this inner 

 slope or reef-platform varies in the Maldives and Laccadives 

 from half-a-cable to half a-mile. Its surface, especially down 

 to 20 fathoms, is extremely uneven, great buttresses and masses 

 of rock arising to within a few fathoms of the surface. Such 

 rocks are very generally covered with green corals or dark- 

 coloured, calcareous algx, so that except in absolutely calm 

 weather they may not readily be perceived. Further, isolated 

 coral heads — separate coral colonies— may grow up on any rocks 

 within about 20 fathoms of depth almost to the surface. I have 

 in Maldivan lagoons been twice stranded on such heads, arising 

 respectively from 8 and 14 fathoms. At the seaward ends of 

 passages into at<^ls of the same group, where the conditions are 

 not very dissimilar to those outside atolls, similar heads not in- 

 frequently grow from 15 fathoms or even deeper to within 2 or 

 3 fathoms of the surface. The tops of these are often only a 

 few yards across, so small indeed that they may be easily missed 

 in any survey, however careful. 



It is apparent then that dangerous rocks may arise on any 

 part of the reef-platform. The outer steep slope is often so 

 precipitous that the edge of this platform is only separated by a 

 few yards from the loo-fathom line. The latter is usually very 

 carefully charted, but for safety liners and deep-draught steamers 

 should pass well tib seaward of it. J. Stanley Gardiner. 



Gonville and Caius College, Cambridge, April 20. 



Rearrangement of Euclid Book I. 



I HAVE always taken it for granted that the chief, if not the 

 only, objection to Euclid's Elements as forming an introductory 

 course in geometry is that a very large proportion of beginners 

 art unable lo work riders for themselves, and consequently they 

 are reduced to the necessity of merely reading up the proposi- 

 tions in such a way as to be able to reproduce them more or less 

 mechanically in the examination room. 



This difficulty does not exist in algebra because, taking simple 



NO. 1695, VOL. 65] 



equations as an instance, it is easy by varying the numerical co- 

 efficients to furnish the beginner with an unlimited variety of 

 numerical examples which, being all solved by the same 

 method, do not present such difficulties as Euclid " riders," 

 each of which is practically a separate problem or theorem re- 

 quiring a different method of solution. 



The wide gap between the reproduction of bookwork and the 

 devising of methods of solving riders presents a serious obstacle 

 to the progress of beginners. What I at present fail to see is 

 how the gap would be bridged over either by a rearrangement 

 of the propositions in Book I. or by any of the substitutes for 

 Euclid which have been suggested of recent years, and I much 

 hope that this letter may be the means of eliciting fuller informa- 

 tion on the direct connection between the present unsatisfactory 

 state of affairs and the proposed remedies. G. H. BRYAN. 



Bangor. 



The Morphology of the Pleuronectidae. 



Absence from Liverpool has prevented me replying to Mr. 

 J. T. Cunningham's criticisms of the work on the anatomy of 

 the Plaice recently published by Mr. Johnstone and myself. 

 The passage which Mr. Cunningham chiefly objects to is as 

 follows : — " If [the dorsal fin] occupies the mid-dorsal line of 

 the head, then it is obvious that the left eye must have actually 

 passed through the substance of the head to reach the ocular 

 side. This supposition, absurd as it may seem to us now, was 

 in fact believed by such an observer as Steenstrup. " In "cor- 

 recting" this passage Mr. Cunningham says: — "The truth of 

 the matter is that Steenstrup did not believe any supposition, 

 absurd or otherwise, on the subject, but stated from actual 

 observation that in certain larval Pleuronectida; the eye of one 

 side passed through the tissues of the head and emerged on the 

 other side. The form in question was long known as Plagusia, 

 and is now known to be the larva of Rhomboidichthys. The 

 truth of Steenstrup's observations was fully confirmed by 

 Alexander Agassiz at Newport, R.I." 



Now on referring to Steenstrup's memoir again I find that it 

 is Mr. Cunningham himself who has misunderstood that author. 

 For whilst Steenstrup certainly observed an apparent passage 

 of the eye through the head, he also supposed that the eye 

 passed actually through the tissues of the head itself, as apart 

 from those of the dorsal fin, which cannot, of course, be con- 

 sidered a part of the head. This is the theoretical deduction 

 that I characterised as absurd, since it is needless to say that 

 neither Steenstrup nor Agassiz ever witnessed so impossible a 

 phenomenon. Indeed, both Agassiz and Ehrenbaum state, 

 quite correctly, that the migrating eye lies between the base of 

 the dorsal fin and the roof of the head, and therefore only 

 "apparently passes through the head" (Agassiz). 



The significance of the asymmetry of " Plagusia" has been 

 made quite clear by the short but important paper recently 

 published by Nishikawa. This paper renders almost certain 

 the deduction which I think most morphologists would have 

 drawn from Agassiz's work, viz., that the metamorphosis^ of 

 Plagusia is in all essential respects similar to that of the Plaice. 

 The fact that here the dorsal fin grows forwards before meta- 

 morphosis sets in has not affected the fundamental character of 

 the torsion, for the migratory eye is, of course, morphologically 

 outside the head during the whole of its transit. Nishikawa 

 says, and very truly :— " In every case, the passage of the eye 

 from one side to the other in flat fishes is morphologically along 

 the dorsal surface of the head." The statement, therefore, to 

 which Mr. Cunningham takes exception is absolutely correct, 

 and it seems that, living remote from scientific libraries and 

 doubtless unable to consult the original, Mr. Cunningham's 

 memory has led him astray. 



Mr. Cunningham's second point involves an academic issue 

 that I must leave others to discuss. Prof. Mitsukuri once 

 remarked to me, in connection with his having undertaken some 

 systematic work, that he had temporarily abandoned the morpho- 

 logical pursuit of similarities, in favour of the systematic search 

 for differences. Thus, whilst many systematists, with their 

 taxonomic details, would widely separate the Pleuronectidae from 

 the GadidiC (although Jordan and Evermann, whom we followed, 

 do not), most morphologists, taking a much broader if less pre- 

 cise view of the question, would say that a Plaice was simply an 

 asymmetrical cod-fish. .And both may be right judged by their 

 own standards. F- J- Cole. 



University College, Liverpool, April 14. 



