Among collections of meiobenthos from some sub-littoral muds off the coast of Scotland were eighty-five species of Copepoda. Twelve of these were found to be new species of Harpacticoida. In addition, the hitherto unknown males of four species were discovered.

The Lower Carboniferous genus Prosagenodus Romer and Smith 1934 is re-examined. The type species Prosagenodus interruptus is re-assigned to the genus Ctenodus and a new genus Tranodis named for the American species, of which new material is described. The new species Ctenodus romeri is described, the new genus Straitonia is described, and the bearings of all these discoveries upon consideration of the phylogenies of Ctenodus and Sagenodus is discussed.

The introduction contains an appreciation of the work of James Ritchie (1882–1958) on hydroids. His collections in the Royal Scottish Museum consisting of 266 species have been re-examined and listed with up-to-date synonymy, this also serving as a catalogue of all the identified hydroid material in this Museum.

Among the important collections are those made by W. S. Bruce in the Scotia and E. H. Shackleton's Antarctic Expeditions; there is also much valuable secondary material, especially in the form of micro-preparations, from collections reported on by Ritchie, notably those of the Australian Thetis Expedition, the Scottish Loch collections of Sir John Murray, the Indian Museum and collections by Cyril Crossland, James Simpson and Rudmose Brown and others.

Ritchie described many new species and varieties and all the type material has been noted, lectotypes being designated where necessary.

Hydroids from the Goldseeker collections of the Fishery Board for Scotland were not reported on by Ritchie although he identified a considerable number of samples from Scottish waters—these have been included in this survey. These new records are of considerable value for compiling distribution lists. Apart from Ritchie's own work little has been done on hydroids from waters around the north of Scotland since the days of Hincks, Allman and Norman. The bibliography contains a full list of James Ritchie's hydroid papers.

Literature is reviewed in relation to particular Scottish problems. The individuality of water bodies and methods of harnessing available power necessitates individual treatment. Some general conclusions can, however, be drawn.

The creation of impoundments and the raising of lake levels are considered in terms of the effects on agriculture, rare plant and animal species, lake plankton production, introductions and the growth of fish.

The consequences of fluctuating lake levels are reviewed with reference to the productivity of shallow water communities, bottom animals and the growth and reproduction of fish.

Pollution, changes in temperature and chemical factors, and alterations in the volume and stability of rivers are considered.

Anadromous fish conservation measures include guarantee of minimum river flow, provision of freshets, construction of fish passes, erection of smolt screens, passage of smolts through turbines, creation of artificial spawning gravels, use of hatcheries and the opening up of previously unutilized natural spawning gravels.

In general, hydro-electric schemes have a depressing effect on biological productivity. This effect may be lessened through the application of gained knowledge and experience. Fundamental research into this branch of applied ecology is needed.

Loch Lomond is divisible into two natural regions, a northern, deep, steep-sided trough and a southern, relatively shallow expanse. These are separated by what is, in many respects, a transitional middle region. This topographical diversity has engendered widely different environments for the benthic fauna, especially for the profundal fauna.

A survey of selected sites in each region has shown a distribution of species in accordance with the individuality of these major divisions of the lake.

Chironomid midge larvae and the bivalve mollusc, Pisidium, each have dominant species in different regions. Of the former, Sergentia coracinus characterizes the northern and species of Tanytarsus the southern region; both being absent from the transitional region where Chironomidæ of any species are few in number.

Pisidium conventus predominates in the deep cold waters of the northern and middle regions and is replaced by other species, chiefly P. lilljeborgi, in the southern.

Regional differentiation of oligochaete worms appears to be less clearly defined but with Limnodrilus sp. avoiding the deep water and Stylodrilus heringianus favouring it.

Despite marked differences in proportions of the component species, tentative estimates of biomass of the profundal benthic animals show a tendency towards equality in all regions.

James Murray published in the years 1905–1913 nineteen papers describing about one-sixth of all known species of Tardigrada; an important part was based on the collections of the Lake Survey (1904–1906) and a part of his collections is still present in the Royal Scottish Museum but the rest of his material could not be traced.

The present paper reviews all the new species described by James Murray from the Lake Survey and for each species the type locality is fixed, some complementary descriptions are given and wherever possible lectotypes have been selected.

An account is provided of the external and skeletal features of a four-days old Callimico gœldii, one of twins born in captivity. Bodily proportions are compared with those of other newborn marmosets and tamarins. Diffeiences in pelage from the adult are outlined. Data are provided on the regional external anatomy. The state of skeletal ossification and dental development are discussed. The taxonomic position of Callimico within the Hapalidæ is confirmed.

Human aortic elastin, purified by autoclaving and alkaline extraction, has been resolved by ultrasonic treatment into individual filaments, which appear, in the electron microscope, to be of constant diameter (25 Å) with junction points at fairly regular intervals (1300)Å.

Amino acid analyses on fœtal, normal and old adult elastin showed that the desmosine(s) content remains constant at 3 residues per 105g. of protein which is equivalent to 1100 Å intervals between successive residues, assuming that these are evenly spaced along the polypeptide chain(s). On the other hand the amino acid composition was found to change with age. Thus the aspartic acid and glutamic acid contents increase from 3 and 19 to 11 and 27 residues respectively; histidine and methionine, which are both absent from fœtal elastin are present in small but definite amounts (2 and 3 residues respectively) in older elastins. The lysine content is 9 residues in fœtal elastin and 6 residues in older elastin. Probably the most remarkable feature of this protein is the high content of non-polar amino acids; of 1100 residues in 105g. protein about 1000 (including glycine and proline) have hydrophobic side chains.