September 23, 1920] 



NATURE 



105 



they are of infrequent occurrence, that the change 

 is definite from the beginning, that some at least 

 are recurrent, and that the difference between the 

 old character and the new is small in somj 

 cases and greater in others. But their origin 

 remains obscure. As to their supposed "chance " 

 character, it is pointed out, very usefully we think, 

 that the degree of development of any character 

 increases the probability of further stages in the 

 same direction. Species are to be thought of as 

 groups of genes, and related species have a good 

 many genes in common. Thus similar mutations 

 are likely to occur in different but related species. 

 Of this, indeed, studies on Drosophila have fur- 

 nished experimental evidence. 



We do not know how many books on heredity 

 Prof. T. H. Morgan has written. Their succes- 

 sion marks the rapid advance of a department of 

 science to which his personal investigations have 

 made very important contributions. 



New County Histories. 



The Victoria History of the Counties of England: 

 Hampshire and the Isle of Wight. Part i., 

 pp. 46+2 maps. Part xv., pp. 409-470 + 

 I plate : Buckingham. Parts iv. and vi., pp. 177 

 -205 + map and plate. Part xxiii., pp. 312 — 

 372 + 5 plates: Hertford. Parts ii. and iii., pp. 

 43-221+ map: Berkshire. Part ii., pp. 27- 

 68 + map. Part iv., pp. 173 -196 + map and 12 

 plates: Surrey. Parts i.-iv., pp. 254+4 maps 

 and 2 plates. (London: Constable and Co., 

 Ltd., 1920.) Prices various. 



" '"p'HE Victoria History," finely conceived and 

 I. excellent in performance, at the outset in 

 igoo largely disdained plebeian methods of adver- 

 tisement. Wealthy country gentlemen were often 

 left in ignorance of its existence, and slender 

 purses were mocked by the high cost to be pledged 

 for the history of any single county. A more con- 

 siderate policy has now been adopted. Essays by 

 eminent specialists can be purchased separately. 

 Comparison with earlier county histories shows a 

 surprising advance in recogfnising the importance 

 of natural knowledge. 



Since Nature makes merry with man's artificial 

 boundaries, a work taking all our English counties 

 in detail cannot avoid some overlapping and repe- 

 tition in dealing, for example, with botany and 

 butterflies, with mice and their alliterative con- 

 trast, men. The difliculty is enhanced in zooPogy 

 by the hordes of insects. Records stating when, 

 where, and by whom each species was captured in 

 a particular county become rather appalling. It is 

 NO. 2656, VOL. 106] 



a relief to read in the " History of Surrey" that out 

 of 3000 British flies (Diptera) only a miserable tale 

 of 360 can be credited to the county. Yet this luck 

 is "solely due to the paucity of collectors of this 

 order of insects" {p. 151). Though Diptera be 

 few, "the Phytophagous hymenoptera, i.e. saw- 

 flies, wood-wasps, and gall-flies, are abundant 

 throughout Surrey." Avoid, however, speaking 

 disrespectfully of saw-flies. " Saw-flies can easily 

 be bred and reared in captivity, and it is only by 

 doing this in large numbers that we can hope to 

 arrive at the laws which control that most 

 mysterious phenomenon, parthenogenesis." Mr. 

 Chawner further declares that a common species, 

 Foecilosoma puteolum, produces females only, 

 arguing from the experience that several thousands 

 have been bred for six years in succession, and 

 all turned out to be of that sex (p. 91). Still, it is 

 hard to prove a negative, even for broods to which 

 Sir Ray Lankester's term "impaternate or father- 

 less " would seem appropriate. 



The botanists agree that " the best division of a 

 country for botanical purposes is into river- 

 basins" ("Hertfordshire," Hopkinson, p. 48); to 

 explain the distribution of the flora of Berkshire, 

 "various botanical districts essentially based on 

 the river drainage" are used by Mr. Druce 

 (pp. 29, 51); so also for Surrey Mr. Beeby accepts 

 the division into districts founded on the river- 

 basins "as the most desirable in all respects," w-ith 

 exceptions. The grand exception is, as he ex- 

 plains, that "the geological strata run in such 

 remarkably parallel bands from east to west, while 

 the streams run transversely to them, so that each 

 of the principal rivers has its share of each of the 

 formations." For Surrey Mr. Lamplugh says, 

 "the geological structure of the county is so 

 simple, and its existing features depend so closely 

 upon this structure, that it forms an ideal tract for 

 the study of the elementary principles of the 

 science." The same might be said of the geology 

 of Hampshire as displayed in the late Mr. Clement 

 Reid's luminous treatise. The map of Surrey 

 shows how you may " walk east and west upon the 

 same formation along the line of ' strike ' from 

 one end of the county to the other ; while if we go 

 southward we soon cross to underlying, and if 

 northward, to overlying beds." 



Space permits only bare notice of an important 

 historical disquisition on " Forestry and the New 

 Forest," by Nisbet and Lascelles; and of the pro- 

 fusely illustrated essays on Early and Anglo-Saxon 

 Man in Berks and Bucks by Shrubsolc, Clinch, 

 and Reginald Smith ; while no attempt can be 

 made to discuss the interesting local history of the 

 "Aylesbury Hundred" of the latter county. In 



