The recent suggestion that natural selection of random mutations is inadequate to account for the major features of evolution is rejected. The pattern of evolutionary development in most major groups, the phenomena of extinction and replacement, the rates of appearance of new major taxa, the continuing vitality of the evolutionary process, the overall randomness of evolutionary history, containing directional change within individual lineages, the nature of natural selection, and the geologic evidence for environmental instability are examined. All suggest that natural selection and random variation are adequate to account for the major features of evolutionary history.

Volcanism began in South-east Devonshire with the extrusion of keratophyric tuffs in the Lower Devonian. The majority of extra ves in the Middle and Upper Devonian are basic spilites but there are intermediate varieties. Volcanism in the Middle Devonian was local and in the Ashprington area appears to have been continuous throughout the epoch. At the beginning of the Upper Devonian keratophyric crystal and vitric tuffs were extruded in the Dartington area. Later in the Upper Devonian the Chipley pillow lavas were extruded: it is shown that these lavas were widespread and may probably be correlated with similar lavas at Pentire Head in North Cornwall. The final phase of volcanism is represented by the intrusion of swarms of sill-like bodies of spilitic dolerites in Upper Carboniferous times. Intrusive and extrusive rocks are distinguished, mapped, and classified petrographically

The property of liquefaction of certain confined, water-logged, unconsolidated sedimentary layers is considered to play an important part in the development of much of convolute folding. Lateral intrastratal laminar flow of liquefied beds, according to flow patterns mainly determined by the distribution of parts of the layers that have remained solid, appears to account satisfactorily for internal folding. Although intra-stratal flow, which can result from a number of causes, may considerably deform the stratification planes of a liquefied layer, there is neither lateral shortening nor a notable change in the thickness of the bed.

The heavy mineral suites of the Trias, Rhaetic and lowermost zones of the Lower Lias in the Vale of Glamorgan of South Wales are described. The northerly coastline of the Mesozoic sea, roughly coincident with the present-day periphery of the Coalfield, consisted mainly of Carboniferous Limestone and in places, the Old Red Sandstone and Millstone Grit. The mineral assemblage at any particular point in the littoral zone was determined largely by the nature of the outcropping rocks of the coastal mainland, the derivation of detritus being very localized. Within this zone some degree of gravity sorting of the detritals occurred, this implying a relatively steeply inclined coastal sea-bed. An off-shore current carried detritus from the Armorican land-mass of Britanny and granite of South-West England to this area where the detritals were dispersed thinly throughout the locally derived sediment.

Ignimbrite steeply intrusive into the basaltic agglomerate of the Kilchrist vent is described. Like the intrusive ignimbrite near Kilchoan, Ardnarnurchan, it shows flow structure parallel to the walls, flow being similarly expressed by the elongation and alignment of the constituent shreds of devitrified glass and pumice lapilli. Fragments of basalt, derived from the vent agglomerate, are sometimes also drawn out in the direction of flow.

An area of high, north-eastward plunge of b-axes has been mapped in Silurian greywackes around the mouth of Strangford Lough, N. Ireland. Reconnaisance over a wider area to the south-west is consistent with the hypothesis that this steep plunge is due to the upward push exerted during the emplacement of the Newry Granodiorite. A near surface extension of the intrusion towards the east-north-east is inferred.

Allogenic biotite flakes, together with fish and conodont remains, are concentrated into bands at particular horizons within Upper Ludlovian rocks of Woolhope and other Welsh Borderland areas; and are present but more scattered within the Aymestry Limestone and Dayia Beds. Metamorphic rocks of Malvernian type appear to have provided the source of the biotite.

Quartz-magnetite rocks occur as lenses in an area of migmatitic mica gneiss and have acted as resisters to deformation as well as migmatization. Due to plastic deformation in the enclosing gneisses a quartzite lens now strikes perpendicular to the trend of other resisters which are abruptly truncated.

The quantitative distribution of the alpha particle activity in rocks and minerals by nuclear emulsion techniques is applied to some exceptionally fine-grained rocks. The distribution of radioactivity is comparable to that observed in the coarser-grained rock types more suitable to nuclear emulsion studies.