The experiments described in the present paper were undertaken as the outcome of an investigation into the possibility of securing nodule formation on leguminous roots cultured separately from the shoots. During that investigation it soon became clear that experiments on whole plants were necessary, in order to test the effect, on the nodulation of the normal whole plant, of certain conditions under which nodulation of root cultures was being attempted. It is thought that these observations on whole plants, though ancillary to the main investigation (which is still in progress), are of sufficient interest to be published separately. The observations are concerned with the effect of the following conditions or treatments on nodule development in a particular variety of pea:—

(a) Depriving the plant of light;

(b) the presence of sucrose in the rooting medium;

(c) the presence of nitrate in the rooting medium; and

(d) the presence of certain accessory growth substances, viz. aneurin and nicotinic acid, in the rooting medium.

Increasing attention has been paid to dying-out of heather in Scotland over the last fifteen years. The question is of considerable economic importance, owing to the huge areas of grazing involved. Cameron (1937), Morison (1938) and Cameron, McHardy and Bennett (1944) have dealt with the entomological side of the problem. Braid and Tervet (1937) have stressed the necessity of a fuller study of fungi on heather and, particularly, of the heather rhizomorph fungus.

The present work, begun in 1939, was undertaken to determine the identity, parasitism, distribution and characters of the heather rhizomorph fungus and of any other fungi capable of attacking heather in Scotland. The heather rhizomorph fungus proved to be the only one isolated from heather which acted as a parasite. Accordingly, the others were not investigated further.

The work of Auerbach and Robson (1946, 1947 a and b) on mustard gas and related substances has first shown conclusively that chemical substances may be as effective as high-energy radiation in the production of mutations. Subsequently, mutagenic abilities have been reported for a number of other substances (Hadorn and Niggli, 1946; Demerec, 1947 a and b; Vogt, 1948; Rapoport, 1946; Kaplan, 1948). This discovery, however, does not obviate the necessity to search for further mutagenic substances. On the contrary, it raises the hope that more such substances may be found. Only through a comparative study of many chemical mutagens may it eventually become possible to connect mutagenic activity with specific chemical groups or configurations and thus to throw some light on the chemical basis of mutation. Moreover, the indiscriminacy of mutagenic action which mustard gas shares with radiation may not be common to all mutagens: the discovery of a chemical substance with specific action on one or several genes would mean a large step forward in the analysis of the nature of the gene.

Drosophila mutants are usually defined by structural characteristics exhibited by the adult fly. In certain cases (homozygous lethal mutants and female-sterile mutants) the mutant may or may not be defined structurally, but does exhibit the physiological characteristic of death at some stage.

The females of homozygous lethals are sterile, for the F1; represented by the germinal cells, dies with the mother. The term female-sterile, however, is applied to the well-known cases in which the mother but not her F1 achieve imaginal life.

Of the genera of rock-boring lamellibranchs which occur in British waters, Hiatella (= Saxicava) is the commonest. But the method of boring remains obscure, and for this reason the present research was suggested by Professor C. M. Yonge, under whose direction it was conducted. Observations were made during 1945 and 1946 in the Clyde Sea Area and at the Millport Laboratory, while other work on living and preserved material from both the Clyde and Plymouth areas was carried out at the Department of Zoology, University of Glasgow. Acknowledgments are due for assistance in technical problems to Dr H. F. Steedman of the University of Glasgow, for help with the nomenclature of the genus to Mr R. Winckworth, and for much kindness and help to the late Mr R. Elmhirst, Director of the Millport Laboratory.

Previous reports (Black, 1943, 1945) on the resistance of potatoes to the blight fungus (Phytophthora infestans) have shown the existence of at least two major genetic factors (Ra and Rb) in the host, and the occurrence of not less than two strains (A and B) of the pathogen.

From the studies then reported, it was concluded that the two genes had been brought into the potato from different phyletic sources and that one, Ra, when in the dominant state, conferred resistance to strain A, while similarly Rb conferred resistance to strain B.

There are two commonly met with types of defective eggs laid by the domestic hen that result in considerable financial loss to the poultry farmer, and are frequent enough in their occurrence to affect perceptibly the potential food supply derived from the poultry industry.

The first of these results from the inclusion of blood or meat spots in eggs, and the second is the production of eggs so small as to make the majority of them unsaleable—the so-called “Miniature” eggs.

The presence of blood on the yolk of an egg was recorded by Aristotle as early as 300 B.C., and he attributed it to premature ovulation. Later, about A.D. 1600, Fabricius (Adelmann, 1942), during a demonstration of “sanguineous” eggs to his anatomy class, described a livercoloured body included in an egg. The occurrence of blood spots in eggs led both these authors to propound the theory that the yolk was directly formed from blood.

The rapid spread of bracken in some parts of the country has led to considerable investigation into the habits of the plant. But in almost all cases it is the spread of the adult sporophyte which has been described, and little attention has been paid to the insignificant, complementary half of the life cycle—the prothallus. Nor does any attempt appear to have been made to assess the rate of development of the prothallus and the young sporeling. A recent attempt to collect records of the occurrence of prothalli and young sporophytes in the field has shown how seldom they are found, and has emphasised the fact that little is known of the extent to which the plant spreads by the initiation of new colonies from spores (White, 1930).