February 9, 1899] 



NA TURE 



355 



though more or less intermediate in their characters, rarely 

 afford any evidence of reversion. It thus appears that, not- 

 withstanding the "swamping effects of intercrossing," the off- 

 spring of quite distinct varieties sometimes afford no evidence of 

 reversion, and, further, that Galton's law of heredity (which 

 teaches that the intermediate and remote ancestors together 

 contribute one-half of the total heritage of the average offspring) 

 does not appear to hold in the case of highly prepotent animals. 

 In dealing with the second question, experiments are first 

 described in support of the view that there may be complete, or 

 all but complete, reversion to comparatively recent ancestors. 

 [a) A blue and white fantail (a cross between a white fantail 

 and a dark blue cross-bred fantail), when mated with a blue 

 fantail, invariably produces pure white fantails, identical, as far 

 as external characters go, with their grandsire. (//) A smooth- 

 coated white rabbit (a cross between an Angora and a smooth- 

 coated white buck), mated with a smooth-coated and almost 

 white doe (the granddaughter of a Himalaya rabbit), produced 

 a litter of three, one of which is the image of the mother, one is 

 an Angora like the grandmother, while the third is a Hima- 

 laya (with the characteristic black ears and muzzle and dark 

 grey feet and tail) like the great grandmother. 



The following experiment supports the view that there may 

 be reversion to intermediate ancestors : — A Dalmatian dog 

 crossed with a well-bred sable collie produced three pups, which 

 closely resemble young pointers — these pups, with their white 

 ground colour and four or five yellowish-brown patches, in all 

 probability reproduce fairly accurately the intermediate ancestors 

 of the Dalmatian sire. This experiment also suggests that if 

 prepotent ancestors occur along the route which any given variety 

 has travelled, reversion may be at any point abruptly arrested. 

 The remaining experiments detailed afford evidence of more 

 or less complete reversion to comparatively remote ancestors ; 

 ia) An Indian game Dorking cock, crossed with a dark 

 bantam hen, produced, amongst other birds, a cockerel almost 

 identical with a jungle fowl. It not only resembles Galliis 

 bankiva in form and colour, but also in being extremely shy 

 and (unlike the Dorking-like members of the same brood) in 

 its habit of flying away for a considerable distance when 

 .suddenly disturbed. (/') The zebra-horse hybrids hitherto bred 

 are in their markings very unlike their zebra parent. When 

 the sire or dam is a Burchell zebra, the hybrids in the 

 arrangement of their stripes are not unlike the Somali zebra 

 (Eqiitis grevyi), which is, in all probability, in its decoration, 

 the most primitive of all the living zebras. The zebra i -horse 9 

 hybrids {Zebrules), bred by the author at Penycuik, and the 

 horse <? -zebra 9 hybrids (Zcbriniiies), bred at Theobald's Park, 

 Herts, by Lady Meux, differ from the Burchell zebra parents, 

 and agree with the Somali zebra in having (i) rounded instead 

 of pointed arches on the forehead ; (2) more than twelve 

 cervical stripes ; (3) numerous stripes across the loins and 

 croup — instead of five or six broad oblique stripes — and (4) in 

 having the mane extending some distance beyond tlie withers. 



In one of the Penycuik hybrids there are two sets of stripes 

 over the hind quarters. In this hybrid the more pronounced 

 stripes seem to have been inherited through the zebra parent, 

 while the less distinct, which run in a different direction, have 

 in all probability been inherited through the horse parent. This 

 view is supported by the markings usually found in zebra-ass 

 hybrids, in which the dorsal and shoulder stripes and the bars 

 across the legs are, without doubt, inherited from or through 

 the donkey parent, while the majority of the other markings 

 are probably transmitted by the zebra, (i) Mules and hinnies 

 are often more richly striped than their parents ; 6'.^. a hinny 

 recently obtained at Penycuik by crossing a light grey she-ass 

 with a bay Welsh pony has, in addition to dorsal and shoulder 

 stripes, distinct bars across the legs — there are no leg bars in 

 either of the parents. Moreover, this hinny is of a yellowish 

 brown colour, and in many ways seems more primitive than either 

 of its parents, (rf) The nearest approach to complete reversion 

 has hitherto been obtained by crossing pigeons. Darwin, 

 by crossing a barb-fantail with a barb-spot, produced a bird 

 " which was hardly distinguishable from the wild Shetland 

 species." ' 



Referring to this experiment, Weismann says that Darwin 

 devoted his attention to the coloration of the species, and failed 

 to state whether there was complete reversion, i.e. a com- 

 plete agreement in form as well as in colour of the barb-fan- 

 tail-spot with the wild rock pigeon. By way of settling 

 ^ "Animals and Plants," vol. i. p. 210. 



NO. 1528, VOL. 59] 



whether in the case of pigeons complete, or all but complete 

 reversion occurs, the author first crossed an "owl" with an 

 "archangel "pigeon, and then mated the cross-bred bird with a 

 pure white fantail. The owl-archangel cross had neither the 

 frill, short beak, or short round head of the owl, nor yet the 

 crest or bronzed black colour of the archangel. The owl- 

 archangel-fantail cross is almost identical in colour, size, and 

 form with the Indian wild rock pigeon. The only essential 

 difference is in the tail, for though there are twelve feathers (in 

 the fantail parent there are thirty), the tail is slightly arched ; 

 this is the only suggestion of the white fantail sire. 



The author believes that the exjieriments recorded afford sub- 

 stantial support to the reversion hypothesis. 



MASSIVE LAVA FLOWS ON THE SIERRA 

 NEVADA. 



A N account of "Some Lava Flows of the Western Slope of 

 ■^ the Sierra Nevada, California," is given by Mr. F. Leslie 

 Ransome, in Bulletin No. 89 of the United States Geological 

 Survey, 1S98. The area is described as having been worn 

 down to a rough peneplain during the interval between the 

 close of the Jura-trias and the beginning of the Miocene period. 

 The rocks upon which this somewhat uneven peneplain has 

 been carved are those of the so-called " Bed-rock series "' of the 

 Gold Belt, and are of Jura-trias and earlier age. They consist 

 on the lower slopes (or foothill region) of clay- slates, schists, 

 limestones, quartzites and various igneous rocks ; and on the 

 higher slopes mainly of gneissic and granitic rocks. 



Volcanic eruptions began during the Miocene period, and, 

 accompanied by elevation and tilting of the peneplain, lasted to 

 the end of the Pliocene. The first eruptions were rhyolitic, 

 followed by the laying down of a great cloak of andesitic 

 breccias and tuft's. The deposition of auriferous gravels both 

 preceded and accompanied the piling up of volcanic materials. 

 Thus the earlier accumulation of andesitic breccias and tufts was 

 interrupted by at least one period of considerable erosion during 

 which a large stream, the predecessor of the present Stanislaus 

 river, cut through the volcanic cover into the Bed-rock series 

 along the greater part of its course. During subsequent erup- 

 tions massive flows of lava extended over limited areas, 

 displacing the stream before mentioned, and following gen- 

 erally the course of the Stanislaus river, while andesitic 

 breccias and tuffs were spread for hundreds of square 

 miles over the western slope of the Sierra. Other more re- 

 stricted flows of lava followed, and the volcanic period was 

 brought to an end by fresh andesitic eruptions, as shown by 

 breccias which rest on the massive flows of lava. To these 

 lavas the author applies the name of Za/iVt;,, derived from the 

 Italian province of Latium, where there occur in abundance 

 rocks closely related to those he describes. Mineralogically the 

 Sierra Nevada latites are nearly allied to ordinary andesites, but 

 chemically they stand between the andesites and trachytes. 

 They correspond to the plutonic monzonites of Brogger, and 

 represent the eft'usive forms of the magma. The author would 

 use the term latite in a broad sense, and to include such 

 varieties as toscanite, vulsinite, and ciminite, which have been 

 described by Washington in his studies in the Italian volcanic 

 regions. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Oxford. — At the I96lh meeting of the Junior Scientific Club, 

 on February 3, Mr. F. N. A. Fleischmann exhibited a heart- 

 shaped twin of calcite, and Mr. H. B. Hartley gave an exhibit 

 of Japanese sword blades, explaining at the same time the mode 

 of manufacture that has been used since the fourteenth century 

 in Japan. Mr. M. Burr read a paper on " grasshoppers." — The 

 ofticers for this term are— President, Mr. F. Soddy (.Merton); 

 Chemical Secretary, Mr. H. B. Hartley (Balliol) ; Biological 

 Secretary, Mr. A. G. Gibson (Ch. Ch.) ; Treasurer, Mr. W. E. 

 Blackall (Non-Collegiate) ; Editor, Mr. H. E. Stapleton (St. 

 John's); Committee, Mr. F. N. .4. Fleischmann (Magdalen), 

 Mr. E .Gurney (New College), .and Hon. F. R. Henley (Balliol). 

 At the next meeting of the Club (Wednesday, February 

 15), Prof. Odling, F.R.S., will read a paper on "Chemical 



