In a general survey of the pinna-traces of Ferns (Davie, '14), the results of which have been summarised in tabular form (loc. cit., p. 354), two main types of pinnatrace were described and contrasted. In the one—the “extramarginal”—the pinnatrace leaves the back of the hook formed by the incurved edge of the leaf-trace; in the other—the “marginal”—the outwardly directed margin of the leaf-trace is simply nipped off as the pinna-trace. The more primitive Ferns in the evolutionary scale, and the first leaves of both primitive and advanced Ferns, exhibit the marginal type of pinna-trace; the extramarginal type of pinna-trace is found in those Ferns which stand midway between the extreme types in the system of classification, and in some advanced forms.

That there is a decided need for the ecological study of insects and other animals was first brought home to the mind of the author whilst engaged upon the subject of a “General Survey of the Insect Fauna of the Soil” (vide Jour. Econ. Biol., vol. viii, part 3, 1913). Much information has been collected at various times by numerous authors, and especially those who have treated of the habits and behaviour of animals, but very little attempt has been made to systematise the data variously gathered, to explain the cause and effect of many obscure phenomena, or to make important observations accessible for the use of the animal ecologist. Thus, at present, we find ourselves on the threshold of practically a new and undisputed field, with opportunities for original and interesting research extending in innumerable directions. Dr C. C. Adams, now of Syracuse University, New York, who has written a most useful work, “the outgrowth of the effort as it has developed in the study and teaching of animal ecology,” in which is listed most of the literature applicable to the science, says (p. 10): “The associational is the phase of animal activity which may be considered as the form of animal behaviour which has developed into the human social relations,” and concludes that, because of the social character of human society, those interested in matters pertaining to the welfare of mankind, such as the sociologist, the physician, the sanitarian, and the agriculturist, will ultimately participate in a keener appreciation of the associational aspect.

Considerable interest attaches to the unravelling of the complete life-history of the Psilotaceæ, since they are apparently the nearest living representatives of the Sphenophyllales.

The recent description of the gametophyte of Tmesipteris by Prof. Lawson, whose figures 1 had the privilege of seeing before they went to press, and the discovery of the gametophyte of Psilotum, which is the subject of the present paper, form a first contribution to the solution of this problem. It is of some interest to note that there remains now no Pteridophyte the gametophyte of which has not been described.

In the early part of this research I was fortunate in finding a locality near at hand in which Psilotum flourished, and therefore I had at my disposal abundance of spores and later numerous prothalli.

Since the preliminary announcement of the discovery of the prothalli of Tmesipteris and Psilotum communicated to the Royal Society of Edinburgh in June 1916, a considerable amount of additional material has been found, and it seems therefore desirable to place on record a more detailed account of these interesting structures. The preliminary description, as published, was based upon but a few specimens, and these were not sufficient to reveal all of the vegetative and reproductive features, nor enough to justify any broad general conclusions as to the phylogenetic position of the Psilotaceæ. The discoyery, however, has filled in an important and interesting gap in our knowledge; for the Psilotaceæ are the very last of the known Pteridophytes to surrender their gametophytes to the light of science.

As the King Penguin chick grows, the down tassels forming the prepennæ increase in length until they measure from 50 to 75 mm. (2 to 3 inches) over the greater part of the body. Some of the barbs of the juvenile down carry for some time natal down barbs on their tips, and the inner ends of all the barbs forming the tassels are eventually found to be continuous with barbs of either the main shaft or the aftershaft of the developing true feathers. How long the down coat is worn by any given King Penguin is not definitely known—it is said that King Penguins may not moult the prepennæ until they are nearly a year old; neither is it known at what time of the year the majority of the King Penguins living under natural conditions in South Georgia shed their prepennæ, or how long the moulting process usually lasts.

In the year 1861 the ferns collected by Vieillard in the island of New Caledonia were described by Mettenius in a paper entitled “Filices Novæ Caledoniæ” (Ann. Sc. Nat., iv, 15). Among the organisms described was a new and remarkable fern for the reception of which a new Gleicheniaceous genus Stromatopteris was founded. Having noted in particular the absence of roots, and the hairy and sclerotic character of the axis, Mettenius figured the latter as obliquely ascending at its base, but as upright and closely and repeatedly branched more distally. The simply pinnate unbranched leaf was described as a direct continuation of a branch of the axis, with nodular base, slender rachis, and many small leathery pinnæ with sympodial dichotomous venation. With regard to the sori, attention was directed in particular to their development singly on the pinnæ and towards the base of the upper margins, and to the mound-like hairy receptacle which lodged the forking of the basal acroscopic vein. The sporangia, numbering from two to six, were stated to be distributed on the back and towards the periphery of the receptacle; their stalks were short and massive, the annulus complete and transverse, and dehiscence longitudinal and extrorse.

In a previous paper on the anatomy and affinity of Platyzoma microphyllum R. Br. (Trans. Roy. Soc. Edin., vol. li, No. 20, 1916), the structure of a single herbarium specimen of this rare Australian fern, collected by Professor Baldwin Spencer in 1902, at Boorroololoo, N.T., was described. Attention was directed in particular to the remarkable heterophylly, the anomalous stelar structure, and the unique sporangia and spores. The facts detailed made it difficult to indicate any known fern with which Platyzoma could be reasonably compared. They might be considered to suggest a probable derivative position for Platyzoma from some Gleicheniaceous source; but their divergence from the Gleichenia characters was so pronounced that it seemed impossible to retain a view of close affinity between Gleichenia and Platyzoma.

When any one of the following tables has been given in the past to an extent useful at the present time, it will be found by the computer that the necessary volume is only with difficulty accessible and hardly ever to be purchased. That these tables are obviously useful is perhaps all that need be said in justification of their more extended computation.

The two beetles Myelophilus minor Hart, and Myelophilus piniperda Linn, belong to the family Scolytidæ (the Ipidæ of Hagedorn), of the series Rhynchophora or snouted beetles.

The genus Myelophilus Eichhoff has the following characters: (1) the biting edges of the maxillæ are beset with spines, (2) third basal tarsal joint broadened out, (3) head with rostrum visible, (4) funiculus of antenna six-jointed, (5) club of antennæ not quite round but somewhat pointed at the apex, (6) head and thorax with outstanding hairs, (7) front edge of thorax not depressed in the middle.

The theory of the knotting of curves, except for a few elementary theorems due to Listing, was entirely neglected until Tait was led to a consideration of knots by Sir W. Thomson's (Lord Kelvin's) work on the Theory of Vortex Atoms. He attacked chiefly the problem of constructing knots with any number of crossings, and obtained a census of the knots of not more than ten crossings. Those knots which exhibit a special kind of symmetry—the amphicheiral knots—offer certain points of interest.