August 12, 1909J 



NA TURE 



191 



establishments, in eacli case written by the super- 

 intendent — the Royal Laboratory, Woolwich, by 

 Colonel Sir Hilaro Barlow ; the Royal Gunpowder 

 Factory, Walthani Abbey, by Colonel Sir Frederic 

 Nathan ; and the recently re-constituted Research 

 Department at Woolwich, by Major H. Mansell. The 

 history and development of these important Govern- 

 ment establishments will prove of general interest. 

 The Royal Laboratory alone must be prepared to 

 manufacture at short notice some 3000 articles of 

 approved design for war purposes. An interesting 

 comparison of the cost of shells may be quoted. In 

 1849 the finished shell for 8-inch smooth-bore guns 

 alarmed the authorities. It was \\s. ■^\d. The 

 modern 12-inch shell costs about 29?. when com- 

 pleted ! 



One extract may be permitted from Colonel 

 Jocelyn's article on military fireworks. " In the 

 Mathematical Society of London a rule existed which 

 imposed a fine of sixpence on any member who should 

 let off fireworks in the place of meeting." This but 

 reflects the playfulness of the times when Pepys and 

 his friends enjoyed pelting each other and " the 

 people over the wav " with fireworks. 



The book is illustrated with some fine portraits of 

 those who have been prominently associated with the 

 industry, and a number of old illustrations of powder- 

 making processes, which greatly add to the value of 

 the work. Those selected for reproduction are of 

 more general interest than others relating to powder 

 manufacture itself. The recovery of by-products from 

 the carbonisation of wood, as shown in the first illus- 

 tration (Fig. i), cannot fail to be of interest to 

 chemists, as will also the sulphur-refining plant 

 (Fig. 2) with its retort, fume-hood, and condensing 

 chamber. J. S. S. B. 



D.4.V/5H RESEARCHES ON THE EEL AND 

 THE PLAICE.^ 



THE " Kommission for Havunderspgelser." the 

 official body entrusted with the execution of 

 Denmark's share in the international exploration of 

 the sea, devotes a considerable portion of its resources 

 in endeavouring to solve certain important problems 

 connected with the natural history of the eel and the 

 ()laice. These investigations are producing very de- 

 finite results. 



Two papers recently contributed by Dr. Jobs. 

 Schmidt to the " Meddelelser " of this commission 

 considerably advance our knowledge of the meta- 

 morphosis and distribution of the larv» of the eel and 

 other murjenoids. Since the publication of Dr. 

 Schmidt's notable treatise of 1906, in which the dis- 

 tribution of the larvEe of the eel in the Atlantic, west 

 of Europe, was described in detail for the first time, 

 a large quantity of new material has been collected 

 by means of the Danish research steamer Thor. 



The new captures included more than 500 larvae of 

 the common eel, 300 of which were in different stages 

 of metamorphosis. The material previouslv dealt with 

 (in the treatise of 1906) consisted of 265 specimens, 

 only eight of which showed an advance on the lepto- 

 cephalus stage. Taking the captures of 1905 and 



1 Meddelelser fra Kommissionen for Havundersi^gelser. Serie Fiskeri. 

 Bind lii., Nos. I, 3. 5, and 6. 



Nc. I. C. G. Job. Petersen : On the Lar\'al and Post-larval Stages of 

 some Pleuronectidse (Zeugopterus, Arnoglossus. Solea). With two pUtes. 



No. ?. Jo>is. Schmidt : Remarks on the Metamorphosis and Distribution 

 of the LarvjE of the Eel {AngniUa vulgaris, Turl.). With one plate and 

 one chart. 



No. 5. A. C. Jobansen : Contributions to the Biology of the Plaice, with 

 special regard to the Danish Plaice Fishery, iv. Is the Plaice Indigenous 

 10 the True Baltic? With Two text-fieures. 



No. 6. Jobs. Schmidt : On the Occurrence rf Leptocepbali (Larval 

 Mura;noids) in the Atlantic W. of Europe. With two plates and one 

 chart. 



NO. 2076, VOL. 81] 



1906 together, the following is a list of the leptocepbali 

 of murEenoids so far taken by the Thor : — Lepto- 

 cephalus of eel, 790; of Synaphobranchus (deep-sea 

 eel), 126; of the conger, 32; other leptocepbali be- 

 longing to four unknown species, 12. 



Confining our attention to the common eel, it may 

 be said that these new researches throw light on 

 obscure points, amend former statements, and fill up 

 several gaps. The more important new facts may 

 be briefly summarised as follows : — 



(i) In May all the leptocepbali were in stage 1 ; in 

 September they were mostly in various stages of meta- 

 morphosis. This implies that the propagation of the 

 eel is limited in the main to a certain portion of the 

 year, as is the case with most other fishes. 



(2) In September the later stages were found further 

 towards the shore than the earlier stages. This in- 

 dicates shoreward migration during metamorphosis. 



(3) It was found that both leptocepbali and glass 

 eels were larger in the southern than in the northern 

 part of the area of distribution. 



(4) Whereas in the treatise of 1906 calculations of 

 the shrinkage of the larvEe during metamorphosis were 

 based on fragmentary material, belonging to different 

 regions and different years' groups, it is now possible 

 to say definitely that the diminution in length involved 

 in the retrogressive metamorphosis amounts to i cm. 

 This average is based on a large number of 

 measurements of leptocepbali and glass eels from the 

 same region, and belonging to the same year's group. 

 Further, weighings of leptocepbali and glass eels 

 prove for the first time that the metamorphosis in- 

 volves an actual loss of substance, the dry-weight of 

 glass eels being only one-third of that of leptocepbali. 



(5) There is good evidence that the larvae execute 

 diurnal vertical movements in the sea, coming nearer 

 the surface at night than during the day. 



(6) There are places where the larvce of the eel 

 are the commonest fish, just as we find in the case 

 of the different species of gadoids, each of which (as 

 we know from Dr. Schmidt's own investigations) 

 chooses its own conditions of depth, salinity, and 

 temperature for spawning purposes. Thus the specific 

 trait shows itself in the selection of spawning habitat, 

 as well as in anatomical and physiological peculiarities. 



The first and final chapters of this weird and 

 fascinating history have yet to be written. Neither 

 the eggs nor the spawning adults have been found, 

 though there is good reason to believe that the former 

 are bathypelagic, i.e. floating at considerable depths, 

 as is the case with other muraenoids, Argentines, and 

 other deep-sea fishes. The discovery of these things 

 can only be a matter of time and resources. Ships 

 and men are not lacking, apparently. 



In regard to other mursnoids, the recent investiga- 

 tions show that the conger is a more southern form 

 than the eel. Its larvae do not range further north 

 than Rockall, whereas the leptocepbali of the eel 

 extend to the latitude of the Faeroes. The larvae of 

 the conger do not occur over such great depths as 

 those of the eel. They show the same inshore move- 

 ment during metamorphosis, there being a close con- 

 nection between depth and pre-anal length. 



The larvas of the deep-sea eel (Synapliobranchiis 

 pinnatus) were never taken so near the surface as 

 the leptocepbali of the common eel, never higher in 

 the water than 100 metres. In the case of this 

 species there is nothing to suggest shorewards migra- 

 tion. During metamorphosis the larvae sink to the 

 bottom in deep water, where fully-developed eels of 

 this species were caught in large numbers over a wide 

 area of the north-east Atlantic. 



Of the other leptocepbali (four kinds) it is impos- 

 sible to say at present to what species they belong, 



