February jo, igioj 



NA TURE 



43: 



it>o.S. Dr. and Mrs. Vernon have succeeded in pre- 

 _-,enting an admirable account of the progress of 

 science in Oxford from the days when WilHs. 

 Bathurst, Seth Ward, and Robert Boyle held their 

 •meetings at the lodging of Wilkins, Warden of Wad- 

 ham, in which college Sydenham and Wren were at 

 that time undergraduates. The history of the 

 .struggles and ultimate success of the little band who, 

 led bv Acland, Daubeny, and Walker, with help from 

 Pu>ev, resolved that, so far as in them lay. science 

 should take its proper place among the activities.. of 

 Oxford, is carefully and sympathetically recorded. 

 The work of the museum during the fifty years of its 

 existence — work as>ociated with the names of 

 Phillips, Brodie, Prestwich, Rolleston, Moseley, 

 Lankester, and Burdon-Sanderson, to mention only a 

 few — forms the subject of a specially, interesting 

 cJiapter; and the book ends with an account of the 

 .jubilee commemoration itself. We wish that the 

 authors had found space to include in. their record the 

 address delivered on that occasion by Dr. Vernon 

 Harcourt — an address justly characterised by them as 

 ■■ most instructive and entertaining." Extracts, how- 

 ever, are inc(*porated in the body of the work. 



The book is attractively got up, and illustrated with 

 some good photographic plates, in the legends of two 

 of which, unfortunately, the. points: of the compass 

 are incorrectly given. We reproduce views of the 

 exterior and part of the interior of the orieinal build- 

 ing. F. .\. D. 



THE DISTRIBUTION OF FRESH-WATER 

 EELS.' 



IT is certain that the hydrographers of the 

 Challenger and other deep-sea expeditions made 

 their physical observations in the .\tlantic Ocean 

 depths all unsuspecting of the fact that thereby they 

 were essentially helping to make an important 

 contribution to the natural history of the fresh-water 

 eel. Yet this fact constitutes part of the interesting 

 information derived from a perusal of Dr. Schmidt's 

 latest publication, a continuation of his previous 

 famous researches upon the eel which have previousl)' 

 been described in the pages of N.\ture. 



In spite pf the abundance and wide distribution of 

 the genus Anguilla, the first and final chapters of its 

 life-history, were, until quite recently, matters of pro- 

 found obscurity. It is a fact of common observation 

 and knowledge that the elvers or glass-eels which in 

 th'.> spring months ascend our rivers frequently in 

 countless numbers develop into young eels, and also 

 that adult eels in their silvery breeding dress descend 

 to salt water in autumn ; but there, until a few years 

 ago, knowledge ended and conjecture began. It was a 

 common belief in this country that estuaries and 

 harbours probably afforded the spawning places. In 

 ■ 1893 the Italian zoologists Grassi and Calandruccio 

 proved that Leptocephahis brevirostris, a deep-water 

 fish of obscure systematic position taken in the 

 Mediterranean, was really a larval stage of the common 

 eel. Dr. Schmidt and his Danish colleagues, whose 

 energies were first directed upon this particular 

 research because of the economic importance of the 

 eel-fishery in their country, traced the early "elver" 

 stage down to the open sea, and at last, by their deep- 

 water investigations in 1904-5, succeeded in locating 

 an important breeding region off the west coasts of 

 the British Isles at depths of more than 1000 metres. 

 Subsequent trawlings have revealed the distribution of 

 the early (Leptocephalus) lar\'al stage in the Atlantic 

 • Ocean from the Faeroe Islands to Gibraltar, but always 



■ On. the Distribution of the Fresh-water Eels (Anguilla) throughout the 

 World, (i) Atlantic Ocean and Adjacent Regions. A Biogeogr.-iphic3l 

 Investigation. By Jobs Schmidt. With one chart. Pp. 45. (Copenhagen, 

 1909.) 



NO. 2102, VOL. 82] 



in water of more than looo metres depth and not less 

 than 7° temperature. From these investigations, Dr. 

 Schmidt came to the conclusion that "in order to 

 propagate, this species demands certain e.xternal con- 

 ditions (chiefly great depths with high temperature 

 and salinity of water)," and it was to test the validity 

 of this conclusion for other parts of the w'orld that the 

 research upon the geographical distribution of the 

 fresh-water eel was commenced. 



The .A.nguilla genus is widely distributed, being 

 found in the -Atlantic as well as in the Indian and 

 Pacific re.gions. However, the main point of this 

 inquiry will be best indicated by limiting our consider- 

 ation to the regions of .\merica, Europe and .Africa 

 where most data are available, and where (if we except 

 eastern .Africa) the question is simplified by being 

 confined to two species only, viz. Anguilla vulgaris, 

 the European species, and .4. chrysypa, the .\merican 

 form. Now fresh-water eels are entirely lacking on 

 the Pacific shores of North and -South America (and 

 of course in the river systems which have their outlet 

 on this coast). On the Atlantic side, however, they 

 are abundantly represented in the easternmost parts 

 of Canada and the United States, and are found froiti 

 southernmost Greenland and Labrador to the Wes-t 

 Indian .\rchipelago and Guiana. On the other hand, 

 they are lacking in South America south of Guiana, 

 no single record, for example, occurring of the presence 

 of fresh-water eels in the large river systems of Brazil 

 and .\rgentina. They are found on practically all the 

 islands of the .Atlantic north of the Equator 

 (Bermudas, Azores, Madeira, Canaries, Iceland, &c.), 

 and, what is especially worthy of attention, they 

 occur on islands where other fresh-water fishes are 

 completely lacking. On the eastern side of the 

 .Atlantic they are found from the region of North Cape 

 and southwards along all the coast of Europe, on all 

 coasts of the Mediterranean, and on the north- 

 western part of the coast of Africa. In Senegal they 

 disappear, and are absent from all the rest of the 

 west coast of .Africa as far as Cape Colony, where the 

 Indian Ocean species begin to be met with. 



Thus in tropical, temperate, and even Arctic regions, 

 .Atlantic fresh-water eels are found — truly a wide- 

 spread habitat, and one affording extremely varied 

 environments! But it is on account of "this 

 astonishing power to submit to most varied outer 

 conditions " that their absence from certain regions is 

 apparentlv incomprehensible. Why, for example, have 

 thev not been able to penetrate further southwards 

 along the coasts of the -Atlantic? In order to under- 

 stand this, it is necessary to recall some of the results 

 of later years' marine biological investigations, 

 especially " the ascertained fact that very often the 

 sensitiveness of a species of fish to its surroundings 

 differs a great deal in its growth-period and in its 

 spawning-time, so that during the latter its require- 

 ments as regards the outer conditions (depth, tem- 

 perature, salinity) are much more definite and very 

 different from those during the first, the effect of 

 which is that the distribution during spawning-time 

 may often be very different from that during 

 growth. . .. It is in the first instance the require- 

 ments as regards the outer conditions during spawn- 

 ing tinie which influence the distribution." 



The earlier investigations upon the spawning places 

 of the eel have shown that in order to be 

 able to propagate, the European fresh-water eel 

 requires great depth (at least looo metres), a 

 high salinity (more than 35'2 per cent.) and 

 temperature (more than 7° C.) at this depth ; and 

 this is where the importance of the hydrographical 

 data obtained from the temperature curves of the 

 Challenger, Valdivia, and other deep-sea expeditions 

 comes in. It is shown that "the absence of eels in 



