4 I2 



NA TURE 



[March 5, 1903 



birds, many of them mere visitors. Of the forty-two 

 species of Entomostraca, only seven are recorded as 

 pelagic, but a large number occur in the deep region. 



Of the twenty-six Rotifers recorded, the majority, 

 fifteen, are pelagic. It is probable that further work in 

 the littoral region would considerably extend the list. 

 Many species of Rhizopods extend into the abyssal 

 region, and several are peculiar to it. Among the Algae, 

 the Diatoms are very numerous, comprising a greater 

 number of species than any other group of organisms, 

 while, on the other hand, the paucity of Desmids is 

 remarkable. Only two species of Closterium represent 

 the typical unicellular group ; the only species cited as 

 pelagic is a Hyalotheca, while the genus Staurastrum, so 

 generally present in the plankton of the lakes in this 

 country, is not noted at all. 



It is somewhat surprising to find only two Hepatics and 

 three Mosses in Prof. Forel's lists and no Lichens what- 

 ever. In dealing with the Mosses, the professor seems to 

 make it a rule only to admit species which are per- 

 manently submerged, a rule which, applied all round, 

 would greatly curtail his lists. 



The second half of the book is devoted to the study in 

 •detail of the plant and animal associations of the various 

 regions and to the discussion of many interesting 

 problems offered by the life of the lake. Into most of 

 these problems, concerning the origin of the various 

 associations, the migrations of the plankton, &c, we 

 cannot here enter, but several of the more interesting 

 points may briefly be noticed. 



Prof. Forel insists on the recent origin of the flora and 

 fauna of the lake, in common with those of all regions 

 which have undergone a glacial epoch. He remarks on 

 the cosmopolitan character of the pelagic population. A 

 remarkable fact is the occurrence of Chironomid larva; 

 and air-breathing Molluscs at great depths. Without 

 any apparent modification of their structure, both these 

 animals seem to be able to adapt themselves to the 

 altered conditions found at the bottom in the deeper 

 parts of the lake when casually transported thither. 

 When brought to the surface, the air-tubes and air-cavity 

 are found to contain water. After exposure for some 

 time in shallow water, they resume the normal mode of 

 breathing. Prof. Forel further points out that those 

 Chironomid larvae which had become adapted to breathe 

 water would thereby be prevented from rising to the 

 surface to pass into the winged state. He asserts that as 

 a matter of fact they never are observed to emerge 

 from the water except in the littoral region, and dis- 

 cusses the possibility of the insects breeding pedo- 

 genetically, as is known to occur with some species, but 

 considers it more probable that they are all casually 

 introduced. 



Some notes are given of the occurrence of albino 

 cygnets among the broods of swans on the lake. There 

 is also a reproduction of an interesting old plate, dated 

 1 581, from the Library of Geneva, giving sketches and 

 notes of nineteen species of fishes frequenting the lake. 

 Mention is made of a fungoid disease, attributed to 

 Saprolegniaferax, which attacked the pike in the lake in 

 the years 1 886 and 1887, destroying large numbers of all 

 sizes. The work is valuable as a comprehensive summary 

 of the biology of a large lake, and will be of much 

 NO. 1740, VOL. 67] 



service to those who are making similar studies of other 

 lakes. 



The second and concluding part of the third volume of 

 Prof. Forel's monograph on the Lake of Geneva will, it is 

 understood, deal with the pile-dwellings, fisheries and 

 other relations of man to the lake. 



OUR BOOK SHELF. 



A Monograph of the Land and Freshwater Mollusca oj 

 the British Isles. Vol. ii. Part viii. By J.W.Taylor, 

 F.L.S. Pp. 52; 5 pis. col., figs, in text. (Leeds: 

 Taylor Brothers, 1902.) 



WITH the present part, this work enters on its long- 

 awaited second volume, containing the systematic 

 portion. The first volume was devoted to a sort of 

 general introduction to the study of the Mollusca, with 

 special reference to British forms, and left much to be 

 desired : but this second section should prove of great 

 value, seeing that for many years past the author, ably 

 seconded by Mr. W. D. Roebuck, has been patiently 

 amassing a large amount of very valuable information 

 concerning the distribution and variation of the British 

 non-marine Mollusca. So extended, however, is the 

 plan on which the work is projectefl that further co- 

 operation is invited and will, we hope, be readily given. 



As compared with other works of its kind, the present 

 one is noteworthy for the greater length at which the 

 various details concerning each species are treated and 

 for the introduction of new features of great importance. 

 Anatomy receives its proper share of attention ; but too 

 much space is bestowed, and mostly wasted, on varia- 

 tions that are quite unimportant scientifically. In this 

 section especially, more careful editing is required to 

 remove the too obvious traces of mere compilation and 

 to introduce a better sense of proportion between the 

 different parts. 



The geographical distribution of the species is, how- 

 ever, the strong feature of the work, and here an innova- 

 tion of very great value is introduced, for, besides 

 detailed records in the text, the range of each species in 

 the British Isles is shown on a separate, coloured map, 

 indicating (a) districts from which the author has actually 

 seen specimens, (b) areas for which the species has been 

 recorded by other observers, and (c) regions in which it 

 probably occurs. To these we hope the author will add 

 indication (say by dots) of districts formerly occupied by 

 a species (e.g. Acanthinula lamellatd] the range of which 

 has become restricted in recent times. Distribution over 

 neighbouring areas of the continent is shown on maps 

 in the text. 



The inclusion of forms entirely fossil {e.g. Glandina 

 from the Eocene) is another, welcome, new departure, 

 and here, as in the geological histories, we believe, 

 although it is not so stated, Mr. R. B. Newton rendered 

 some assistance I cf. Journ. Conch., x. p. 74). 



The illustrations in the text are mostly good, but here 

 and there is one unworthy of the rest (e.g. No. 52). 



Plate i., with coloured figures of Testacella, is an ex- 

 cellent example of tri-colour printing, but the artist must 

 surely have had wooden models to draw from. 



One would have expected to have found a more modern 

 classification adopted than that set forth on the opening 

 page, but what was selected should have been correctly 

 followed. The branch Euthyneura, which was established 

 by Spengler, and not by Lankester as stated, is not syno- 

 nymous with the order Pulmonata, which is only one of 

 its subdivisions. 



These and other minor blemishes, however, do not 

 affect the value of the work in its entirety, and when 

 completed the author will undoubtedly have made a 

 most important contribution to the literature on the 

 studv of our British non-marine Mollusca. (BV) 2 , 



