Dec. 31, 1S.85] 



NA TURE 



The Hyracotlierina: are here made the parent stock 

 from which are supposed to have arisen, on the one side, 

 the horses, through the Palsotheria ; the tapirs being an 

 offshoot from an ancient group, the Chahcotheridae. On 

 the other side the rhinoceroses have arisen from the 

 Lophiodonts, from which also the Hyracodonts are to be 

 traced. 



Time alone will show whether the systems of classifica- 

 tion proposed by Prof Cope are founded on sufficiently 

 important characters to render them permanent. It is 

 probable that naturahsts will hesitate before accepting 

 such sweeping changes, especially as they necessitate the 

 adoption of so many new ordinal names. However, it will 

 be well to wait until we have had time to make our- 

 selves thoroughly acquainted with the details of this 

 work, before criticising that which is the result of years 

 of patient labour. We are certainly under deep obliga- 

 tion to the author for his careful and systematic marshall- 

 ing of the multitude of facts with which he has had to 

 deal ; and congratulate him, as well as the directors of 

 the two Sur\-eys, on the successful completion of this first 

 half of the work, which will be a lasting testimony to the 

 zeal and devotion of all who have shared in the labour of 

 its production, and an enduring monument to its author's 

 scientific skill and untiring energy. 



E. T. Newton 



THE DEPTHS OF ALPINE LAKES 



La Faunc profonde des Lacs suisses. Par le Dr. F. A. 

 Forel, de Morges, Professeur \ I'Acad^mie de Lau- 

 sanne. (Bale, Geneve et Lyon : chez H. Georg, 1885.) 

 pROFESSOR FOREL, of Morges, already so well 

 known by his numerous pamphlets and short notices 

 on various points in the natural history and the physical 

 geography of the great lake beside which he lives, has in 

 the present work given us the results of the labours of 

 many years, casting into one mass the many fragments 

 and gathering together and correcting where needful the 

 many interesting papers which alone he has hitherto 

 published. 



It is a small quarto volume of over 200 pages, with a 

 table of contents and a long bibliographical list appended ; 

 it is a pity that there is no index, and the value of the 

 work would have been greatly enhanced had it been 

 illustrated with figures of the new or rare species, and 

 especially with a map of the basin of one at least of the 

 Alpine lakes. Though it professedly deals with the deep- 

 water fauna of the Swiss lakes as a whole, and though 

 frequent allusions and references are made to work done 

 by Prof. Forel and others in a very large number of these 

 and of other lakes, this memoir, as is natural, deals most 

 fully with the fauna of one lake only — the Le'man. Of 

 the only other great lake on the northern slope of the 

 Alps— the Bodensee — and of the great lakes of the 

 southern slope — Verbano, Lario, and Benaco — we are 

 told but little. This is, however, a matter of the less 

 importance as the physical surroundings which have 

 affected the fauna of the Ldman are almost exactly 

 repeated in the other lakes, and the little that is 

 known of their deep-water life is very similar to w^hat we 

 know of that of the Lcman. Of this— his own lake — 



study which may be called 



Prof. Forel has given us 

 complete. 



The chief agents affecting the life of the lake are tem- 

 perature and light : of less importance are the shape and 

 capacity of its basin, the matters dissolved in or held in 

 suspension by its waters, the movements — for the most 

 part superficial — to which its waters are subject. And 

 light is a far more important factor than temperature, — it 

 is at a depth of 30 metres, at the depth that is to say at 

 which chlorophyll-forming vegetation ceases that Prof. 

 Forel draws the line separating the littoral and deep 

 regions of the lake : the actinic action of light ceases 

 at 50 metres in summer, at 100 metres only in winter, 

 owing to the greater transparency of the waters at that 

 season. 



Speaking of the conditions of this deep region Prof 

 Forel says : " They all tend to calm, to rest, to absence of 

 movement. Uniformity, monotony, equality, no motion, 

 no variation, such are the general characters of this 

 region, with which we can compare no other region but that 

 of the deep sea." It is after having studied the flora and 

 fauna of this region almost uninterruptedly for six years 

 that he now gives us what he modestly calls a sketch of 

 the' results at which he has arrived. 



But in order to be able properly to understand the 

 deep-water life of the lake we must first be properly 

 acquainted with the inhabitants of the upper waters, 

 whether of the shore or of the open. To this end, the 

 first half of the book is occupied with a careful account 

 of the littoral and pelagic flora and fauna. The most 

 interesting point in this section is the statement that the 

 same species of pelagic Eutomostraca are common not 

 only to the Alpine lakes but to those also of Scandinavia 

 and the Caucasus. They exist in enormous numbers, 

 thousands of individuals may be captured in one sweep 

 of the net, and they form a very important part of the 

 food of fishes, giving to them, it appears, their charac- 

 teristic fishy smell ; but the species are few. The very 

 wide distribution of these few species is probably brought 

 about by migratory water-fowl. 



The deep-water flora of the Leman finds its lowest 

 Hmit at a depth of 100 metres, and consists entirely of 

 Algffi, chiefly Palmellace^ and DiatomacejE, of which the 

 latter are the most abundant in species, but the Palmel- 

 laceae are the most important, forming in many places a 

 felted carpet on the surface of the ooze, and thus giving a 

 more solid bottom, on which animals may move or in 

 which they may live. 



The population is much denser in the upper part of the 

 deep region than in the lower part, but even in the deepest 

 part life is present ; in the upper part hundreds of animals, 

 dead or alive, may often be obtained at one haul. About 

 100 species (22 of which are new) constitute this fauna : — 

 Fishes, 14 ; Insects, 3 ; Arachnida, 9 ; Crustacea, 16 ; 

 Hydroidea, I ; Rhizopoda, 13 ; Cilioflagellatce, l ; Gas- 

 teropoda, 4 ; Lamellibranchiata, 2 ; Annelida, 4 ; Nema- 

 toidea, 3 ; Cestoidea, i ; Turbellariie, 18 ; Bryozoa, i ; 

 Rotifera, 2. 



The greater part of these species are evidently the 

 descendants of the inhabitants of the shallow waters, and 

 differ from them chiefly in being smaller and less brightly 

 coloured ; the eyes are wanting in GyraSor coccus, and 

 have a tendency to disappear in other species ; the shells 



