4i8 



NATURE 



[Ma^ 25, 191 1 



niinutions of length, sex, age, and weight of over 

 20,000 plaice from various North Sea lishuig grounds. 

 The results show clearly that the conditions with 

 regard to nutrition vary Irom ground to ground, and 

 they suggest that a knowledge of these conditions 

 may, in time, enable fishery authorities to increase 

 the productivity of the North Sea by the " transplanta- 

 tion " of fish from grounds on which the growth is 

 slow to other grounds on which tlie conditions of 

 life are more favourable. Dr. Wallace's paper supple- 

 ments that of Miss Lee in that it gives us data which 

 cannot be obtained by ordinary methods of commer- 

 cial statistics, and which are quite essential for the 

 proper understanding of the latter. 



.Mr. Todd's experiments on "covered nets" are de- 

 signed to elucidate the fishing action of the trawl net 

 in respect of the numbers and sizes of fish which 

 escape capture by the mesh employed. The outside 

 parts of the trawl nets used have been covered by 

 other loose nets of narrower mesh, and the fish which 

 have escaped capture by the inner wide-meshed net 

 are intercepted by the outer narrow-meshed net. Mr. 

 Todd tabulates and discusses the results of a number 

 of such experiments. 



Mr. Wollaston gives an account of the first cruise 

 made by an Enj*lish vessel expressly for the pur- 

 pose of determinmg, by means of specially con- 

 structed nets, the distribution of fish-eggs in the c^en 

 sea. The cruise was made in June, 1909, in the North 

 Sea, by the vessel Huxley, and tables are given which 

 show in detail the results of the experiments made at 

 each observation station, while synoptic charts repre- 

 sent the numbers and distribution of the eggs of 

 certain species of summer-spawning fish present per 

 square metre of sea surface in the neighbourhood of 

 the stations. By far the most interesting part of 

 Mr. Wollaston 's paper is that devoted to a description 

 of the methods employed. The net was specially con- 

 structed, and its "constants" were calculated so that 

 it was possible to estimate approximately the average 

 volume of water which was filtered through its meshes. 

 Welcome improvements in the methods of preserva- 

 tion of the fish-eggs caught, so as to avoid distortion, 

 and obscuration of finer details of structure have been 

 developed. The author then proceeds to apply the 

 methods of modern biometricians to the analysis of 

 his data. It has hitherto been impossible, in work of 

 this kind, to avoid the confusion of eggs belonging 

 to closely allied species, since in some cases a fish-egjr 

 can only be identified by measuring its diameter, and 

 that of the contained oil globule. In some pairs of 

 species these pairs of characters overlap, and it was 

 an error of this nature that vitiated (to some degree) 

 the results of Hensen's famous North Sea cruise of 

 1895. ^If- Wollaston, however, elaborates a mathe- 

 matical method whereby the eggs belonging to two 

 such overlapping species can be separated. If in a 

 number of examples of the eggs of one species two 

 measurable variable characters, such as the diameters 

 of the egg- and oil globule, be determined, then the 

 frequencies of these two variables can be represented 

 by an equation, which is that of an elliptic "correla-^ 

 tton surface." But a group of eggs may include two 

 species allied toefether in that the diameters of the 

 eggs and those of the oil globules do not differ g-reatly ; 

 nevertheless it is only by these characters that the eggs 

 mav be recognised. In such a case the correlation 

 surfaces overlap. Mr, Wollaston then shows that it 

 is always possible, by means of relatively simple 

 mathematical methods, to decompose the compound 

 correlation surface so obtained ; and to estimate with 

 a very fair degree of probability the actual numbers 

 of each species of egg in the group. We believe that 

 this method is quite a novel one. 

 NO. 2169, VOL. 86] 



The |)lankton and hydrographic investigations : 

 to the year 190O. .Mr. Bygrave has j^iven the 

 tables recording the distribution and relative d' 

 of the planktonic organisms present in the Cham 

 that year. He shows that the density of oceanic 

 plankton may be correlated with the salinity of th<- 

 water. The seasonal changes takinjj place in th< 

 abundance of the plankton are also discussed, and thi- 

 author adopts Brandt's hypothesis, according to which 

 the sprinj; maximum of density of Diatom and Peri- 

 dinian plankton is the result of the accumulation of 

 food-stuffs in the water durinjj the preceding winter 

 months, while the summer minimum is due to thf 

 activity of denitrifying bacteria, which decompose 

 nitrogen compounds, so that the latter cannot be used 

 uj) by the diatoms. 



The hydrography of the English Channel i« ''•- 

 cussed by Mr. Slatthews in n sho rt paper of 

 general interest. An accounflHRistrated by c!...; . . 

 of the salinity and temperature variations during the 

 year 1906 is given, and the author then discusses the 

 results of calculations of the mean s.'irmities during 

 the years 1903-9. He shows that in addition to the 

 annual salinity variation, there is a two-yearly p)eriodic 

 chanpfe, of such nature that the "even" years are 

 characterised by a hig^h range of salinity variation, 

 while in the " odd " years the range of variation is low. 

 The annual and biennial periods are superposed on a 

 long'er one, probably twelve-vearly. These discussions 

 anticipate a further paper, which promises to be one 

 of very great interest. J. Johnstone. 



A ONE-VOLUME NATURAL HISTORY.' 



'"no compress even a sketchy account of the leading 

 X types of existing animals into a small octavo 

 volume of just over 560 pages, and that illustrated 

 by a number of relatively large figures, is a task of 

 stupendous difficulty. In the present instance the 

 author has increased the difficulty by introducing — 



Fig. I.— a Chinchilla. From the " New Illustrated Natural History. 



probablv in accordance with what I believe to be a 

 mistaken notion on the part of publishers — a number 

 of anecdotes, which merely waste space. This may 

 perhaps account for the ver\- imperfect diagnoses of 

 most of the groups and species, which appear in many 

 cases insufficient for their identification by those who 



1 "New Illustrated Natural Histor>- of the World." By E. Protheroe. 

 Pp. xx+564. (London : G. Routledge and Sons, Ltd. ; New York : E. P. 

 Dutton and Co., u.d.) Price js. M. net. 



