February, 1915. 



KNOWLEDGE. 



59 



Leptocephalus stage of the Eel the haemoglobin of the blood 

 is actually suppressed. (It is noted, in passing, that red 

 prawns from the deep dark waters are not " red " in their 

 ordinary- habitat, but simply dark. No red rays of light 

 penetrate through the upper fiftj' fathoms, and an object 

 cannot look red unless red raj'S of light are falling upon it.) 

 Jlany of the macroplankton animals are phosphorescent, 

 and the pattern of the Ughts may sometimes help in recog- 

 nition. Sense-organs, e.g., balancing organs, are well 

 developed. Flotation is assisted in many ways, e.g., by the 

 gas in the internal shell of Sepia, or by the s^\^m-bladder of 

 fishes. Part of the lining of the swm-bladder can secrete 

 oxygen, and another part can absorb the gas ; thus increasing 

 or decreasing, as occasion demands, the internal pressure. 

 Thus the fish is able to float at one level without effort. 



In the microplankton, such as Radiolarians and Copepods, 

 the problem of flotation may be solved by lessening the 

 specific gravity' of the animal, e.g., by accumulating gela- 

 tinous material in jelly-fishes. Or there may be arrange- 

 ments for gi\"ing increased effect to the \■^scosit^' of the sea- 

 water. This may be brought about merely by diminution 

 in the size of the creature, the ratio of surface to volume 

 increasing with diminution of bulk, or by the development 

 of spinj- or feathery outgrowths. The \'iscosity is lessened 

 with rise of temperature, and thus the arrangements just 

 alluded to are especially well marked in the plankton of the 

 warmer seas. 



SEX RECOGXITIOX IX WOOD FROG.— Arthur M. 

 Banta {Biological Bulletin, Volume XXVI) has tried to 

 discover the method of sex recognition in Rana svlvatica, 

 the wood frog. The males distinguish the females (from 

 other males) at a short distance. There may be something 

 in the diSerences of the sexes in swimming and in beha\-iour 

 when approached, and possibly something in the diSerences 

 in colour. But dead females are distinguished from dead 

 males, and it is suggested that a chemical sense in involved. 

 This should be made a subject of experiment. The males 

 test ever^^ frog or mo\-ing object within a radius of severed 

 feet, and their cold-blooded ardour leads to a good deal of 

 fatal " disharmony." 



SHORE FAUNAS. — Professor A. S. Pearse distinguishes, 

 at Nahant, ]Massachusetts, the rock beach, the sand beach, 

 and the mud flats. The mud flats are marked by the lack 

 of suitable objects for attachment (therefore no sponges, 

 hydroids, and so on), and bj- the comparative impurity of 

 the water (therefore adaptations for respiration, as in Mya, 

 with its long siphon). The fauna of the sand beach is com- 

 posed largely of burrowing animals and those which are 

 continually being swept in. The rock beach is divided into : 

 (1) the rocks above high-tide mark ; (2) the Bala mis zone ; 

 (3) the Ascophyllum zone, with Serlularia pumila, anemones, 

 Purpura, 'Littorina, and so on ; (4) the Fucus zone, with 

 M\ttlus, Balanus, Acmaea, Purpura, Littorina, Asterias, 

 and so on ; and (5) the Chondrus zone, most thicklj' 

 peopled, with Idothea, Acmaea, Asterias, Cancer, Meiridium, 

 and various Bryozoa. 



" Probabl}- no other animal habitat is subject to such a 

 wide range of fluctuations in environmental conditions 

 as the rock beaches along the ocean. The flora and fauna 

 must endure the frigid span of winter and the blistering 

 sun of summer. There is no escape : the tide keeps up its 

 eternal rh}-thm, and the organisms are left exposed to the 

 elements everv time the water recedes. The exposure of 

 the hard substratum to sun, wind, and wave has developed 

 a fauna which consists largely of animals that are : (1) 

 attached permanently or have well-developed clinging 

 organs ; (2) active and hard-shelled or (3) small and 

 ubiquitous ; and (4) mostly very hardy, and able to stand 

 considerable exposure." The animals that have these cha- 

 racteristics most developed have the widest distribution. 



" The surface of the rock is a veritable sieve through 

 which the microscopic organic content of the water dis- 

 appears. The barnacles sweep it constantly with their 

 fishing nets : the carpets of clams siphon food into their 

 depths from the turbid water ; Littorinas search ever\- 

 square inch, and sweep it clean ; wherever there is sufficient 

 moisture the Coelenterates and Brj'ozoans spread their 

 deUcate tentacles to seize their share." There is keen com- 

 petition for food and foothold ; it is a crowded battle- 

 ground ; it has been a great school. It is interesting to 

 compare Pearse 's survey at Nahant with that made by 

 Russell and Iving at Millport, on the Clyde. 



REVIEWS. 



BOTANY. 



Practical Field Botany. — By A. R. Horwood, F.L.S. 

 193 pages. 22 plates. 26 figures. 8-in. x 5-in. 



(Charles Griffin & Co. Price 5 /- net.) 



Mr. Horwood is doing a great deal to popularise the study 

 of botany and to direct those who take it up into the right 

 way. At the same time, his energies are being devoted 

 to preserving, so far as is possible, our native flora from 

 undue diminution or extermination. The present book 

 will cater for those who are led to study plants through the 

 now far-reaching nature-study movement. It deals with 

 the scope, object, and aims of botany ; it describes the 

 various methods o' raountincr plants ; it touche.s on wild 

 flower tables, on museums which are stationary and peri- 

 patetic. It shows what is being done to encourage the 

 study of botany ; and, after dealing with the Ufe-history 

 of a plant, occupies itself with ecologj-, or the association 

 of plants together into what the author calls " formations ' 

 according to soil and situation. This is the kind of botany 

 which appeals most strongly to the general lover of nature, 

 and broadens the outlook of the systematic botanist. 

 No one who reads Mr. Horwood's book can fail to find some 

 suggestion of use and of interest. We heartily wish the 

 work the success which it deserves, and commend it specially 

 to the notice of nature-study teachers. 



\V. M. W. 



CHEMISTRY. 



Essays and Addresses. — By the late J.\mes Campbell 



Brown, D.Sc. 208 pages. 23 illustrations. SJ-in. by 



5f-in. 



(J. & A. Churchill. Price 5/- net.) 



The work of Dr. Campbell Brown included both the aca- 

 demic and the professional side of chemistrj' ; for, in addition 

 to holding the chair of chemistry- in the Liverpool Univer- 

 sity, he was also a public analyst and a consulting chemist. 

 The practical aspect of his work is reflected in the whole 

 of these essa^-s and addresses, which are for the most part 

 of a utihtarian character. They include addresses to the 

 Society of Chemical Industry- on such subjects as " Technical 

 Chemistry- " and the " Ethics of Chemical Manufacture " ; 

 biographical sketches of great chemists ; and historical 

 papers, such as " Chemistry in Liverpool in 1801." 



All of these papers are ver\- readable, even by those with- 

 out any knowiedge of chemistry, especially the last two 

 on " .\nalytical Chemistry' as a Profession " and " Science 

 Applied to the Detection of Crime," which are characterised 

 by their sound common sense and keen humour. 



Some of the opinions, however, are open to criticism. 

 For example, it seems to us that there is some justification 

 for the pubUc attitude towards mistakes made by an 

 analj-st, against which Dr. Brown protests in several 

 places ; as, for instance, on page 202 : " The public can- 

 not forgive a mistake in an analyst. A doctor makes a 

 mistake, and buries it. A lavvyer makes a mistake, and is 



