The paper presents the results of an investigation of the distribution and biology of flies of the family Drosophilidæ in Scotland. Methods of sampling the population are described and notes are given on the breeding of many species in the laboratory. All earlier records of Drosophilidæ in Scotland are brought together for the first time, and the new species, Drosophila silvestris, is described.

Sixteen new species of trilobites are described and named, and thirty species are figured. The specimens were collected from a small exposure of mudstones at Craighead Quarry; most of the species are only known from this one exposure. The occurrence of several species which show strong affinities with forms from higher horizons indicates that the mudstones are more recent than other Balclatchie Group (Lower Caradocian) deposits.

The vertical and horizontal distributions of important plants and animals on exposed rocky shores in Caithness are described, and comparisons are made with other shores of the British Isles. The environmental conditions which cause a marked uplift in the zonation of inter-tidal species in Caithness are considered.

Since the classical work of Sir Thomas Holland at the beginning of this century on the charnockite series in Peninsular India there have appeared numerous papers describing rocks from all over the world which have been claimed to belong to this series. The rocks from the type area around Madras have now been re-examined, with particular reference to their chemistry and chemical mineralogy, to provide further evidence for their mode of origin.

Following petrographic descriptions, fifteen new analyses of these rocks are presented together with trace element determinations, and these are shown to produce smooth curves on a variation diagram. For several rocks all the constituent minerals have been analysed, and it has thus been possible to discuss the mineralogical location of the various major and trace elements in these rocks. Trace element determinations are presented for the 43 minerals analysed together with those for a further 35 minerals not chemically analysed, and their variation within the mineral species is discussed.

The possible modes of origin of these rocks are considered, and from the evidence obtained they are held to represent a plutonic igneous rock series which has undergone recrystallization in the solid state on being subjected to plutonic metamorphism.

From the abounding moraines, drainage features (fig. 21) and other marginal indications an attempt has been made to reconstruct the successive phases of the ice in its retreat into the corries of the Highlands and Islands (Pl. I). Two late-glacial stages are recognised. During the first, the Highland Glaciation, an ice-margin ran from the Orkney Islands across the mouth of the Moray Firth to the Buchan and out to sea north of Aberdeen. Twelve substages (A–L) of retreat, arbitrarily selected, have been traced through the country, except in the Moraineless West where they are unrepresented.

At the maximum of the second stage, the Moraine Glaciation, the ice readvanced to the line stage M (beaded line in Pl. I). The retreat from this line, the inner boundary of the Moraineless West and of the 100-foot raised beach (Pl. I), is divided into nine substages (N–V), based upon a consideration of snowlines. Substage N corresponds to the 50-foot raised beach, substage P to an important readvance.

The snowline throughout the late-glacial period ran in the west parallel with the meridians and rose eastwards. The disposition of the snowlines for stage M is given in fig. 22, p. 900.

The distribution of the ice in the British Isles during the North British, Highland and Moraine Glaciations is represented in fig. 23, p. 923.