Ditylum Brightwelli, a marine plankton diatom, shows very peculiar osmotic relations which have recently been investigated by Gross (1939). The cells (fig. 1) consist of a central mass of protoplasm containing the nucleus and connected by a few protoplasmic strands with the peripheral plasma membrane in which are embedded numerous chromatophores. The remainder of the space inside the cell is filled with cell sap. As in other diatoms, the protoplast is enclosed by a siliceous cell wall. Gross found that Ditylum plasmolyses rapidly in isotonic and hypotonic NaCl and sugar solutions, being reduced in a few seconds to a small spherical body about one-third to one-twentieth of its original volume, similar in all respects to a resting spore. In a solution of NaCl + CaCl2, and in unbuffered artificial sea-water, plasmolysis occurs in all cells, but the process is considerably delayed and completed only after several hours. In artificial sea-water, the pH of which is adjusted to about 8, the cells remain unchanged.

Many studies on the chromosomes of the sheep have been published in the last decade, but their results are unsatisfactory and contradictory, and hence it was found necessary and justifiable to undertake a further analysis, and the present paper reports the data obtained.

The intertidal and shallow-water sands of the coasts of the British Isles contain, in many cases as the dominant amphipod fauna, species of the three genera Haustorius, Urothoë, and Bathyporeia of the family Haustoriidæ, often coexistent in the same habitat and obtainable in the same samples. The swimming and burrowing mechanisms of Haustorius arenarius have been described by Dennell (1933), and I have described (1939) the mechanisms in some species of the genus Bathyporeia. This paper deals mainly with Urothoë marina; no reference is made to the other species of the genus, although U. brevicornis has been examined and found to be similar to U. marina. Since all species of the genus Urothoë are very similar morphologically and live in similar habitats, it may be assumed that the following description of U. marina will apply to them also, but I have had no opportunity of examining the more southern species U. grimaldii or U. pulchella. Crawford (1937) states that the burrowing habits of U. brevicornis and U. grimaldii var. poseidonis are very similar to those of Haustorius.

1. In a previous note (McCrea, 1936) the following problem was enunciated: A rectangular lattice is given; a particle P moves from one lattice-point to another in such a way that, when it is at any interior point, it is equally likely to move to any of its four neighbouring points. P is liberated at any given lattice-point and it is required to find the probability that it will ultimately reach any stated point in the boundary of the lattice, assuming that on arrival at a boundary point its movement ceases.

The fundamental impulse determining the migration of birds is connected with the reproductive cycle; but when that has been recognised it must also be admitted that there are secondary conditions of environment which regulate the actual movements of which a migration is compounded. Of these weather has long been looked upon as one of the most important. There is still, however, much divergence of opinion as to the extent and nature of the influence of weather, and indeed in recent years statistical analysis has led workers, such as Bretscher (1915), to doubt whether any satisfactory connection between meteorological conditions and migration can be demonstrated, and Lincoln to announce boldly that “the state of the weather at any point has little if anything to do with the time of arrival of migratory birds” (1935, p. 59).

In the early part of 1937, during the course of excavations for a sewage extension tunnel at Queen's Park, on the south side of Glasgow, some pieces of bone were obtained by the workmen from a bed of gravel at a depth of 70 feet from the surface. Through the kindness of Mr T. Somers, Master of Works and City Engineer to the Corporation of Glasgow, these remains were loaned to the Geological Survey and, again with his sanction, submitted for examination to Professor James Ritchie of Edinburgh University, one of the collaborators in this note. Professor Ritchie reported that the fragments of bone fitted together to form the greater part of the right radius and ulna of a reindeer. At a later stage of the excavations a portion of an antler was disinterred from the same bed. It seems desirable to record these occurrences in some detail, and for convenience this communication has been divided into two parts. In the first of these the geological position and age of the fossiliferous deposit are briefly discussed, while the second part is devoted to a description of the remains themselves and to a comparison with similar remains elsewhere.

In the course of a recent investigation on the fertilised egg of the mouse (Gresson, 1940 a, b) it was necessary to keep a record of the time at which pairing took place. This revealed that copulation, especially in the winter, was very infrequent during the hours of daylight, and usually took place at about 12 midnight or between midnight and early morning. Similar observations were made by Lewis and Wright (1935), who found that in the autumn and winter mice seldom copulated during the day, and that while the majority of pairings took place between 10 p.m. and 1 a.m., several of their mice paired between 1 a.m. and 7 a.m., whereas in the spring pairing occurred more readily during all hours of the day.

1. This paper is the continuation of a former one (Erdélyi, 1939), and deals with the integration of the system of two partial linear differential equations of the second order

The former paper will be referred to as I; all the notations of I will be retained without further explanation.