The organism which has been found living in the anterior tracheal system of hive bees, and whose presence is associated with Isle of Wight disease, I have identified as a hitherto undescribed species of the genus Tarsonemus. This genus was founded in 1876 by Canestrini and Fanzago, and since then a moderate number only of species has been established. The true systematic position of these Acarines has been much in doubt, and their position in the order has from time to time been revised. Canestrini (1888) constituted the Tarsonemes the type of a special family, the Tarsonemini; they have been associated with the Oribatidæ by Berlese, and with the Cheyletidæ by Trouessart (1892). Banks (1904) regarded them as showing resemblances to the Tyroglyphidse, and placed them in a super-family Sarcoptoidea. An important character of the Tarsonemes is the existence of a tracheal system in the adult female, which is not found in the male nor in any pre-adult stage of either sex. This feature was adopted by Berlese (1897) as the basis of his sub-order, Heterostigmata, and by Oudemans (1906) in his division Trachelostigmata. This super-family includes two families—Tarsonemidæ and Scutacaridæ (Oudemans, 1916). This last is the Disparipedidae of Berlese.

The calciferous glands of earthworms are well-known structures, which occur under a variety of forms, and have been the subject of a considerable amount of research. They are appendages of the oesophagus which occur in different segments in different genera and species; and the usual view of their morphological nature, put forward by Beddard (l) in 1895, and for long generally adopted, is that their epithelium is the oesophageal epithelium thrown into various degrees of folding. Beddard describes these different degrees in a number of different forms.

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 Part I a general account was given of the silicified peat-bed found at Rhynie, and one vascular plant was described in detail under the name of Rhynia Gwynne-Vaughani. Further study has shown that there are two species of Rhynia which we now distinguish as Rhynia Gwynne-Vaughani and Rhynia major. The account in Part I applies to both these species. Along with them there occurs a plant of similar grade of organisation to Rhynia, though quite distinct from that genus: this we name Hornea Lignieri. Asteroxylon Machiei, on the other hand, which will be described in the next part, was a plant of larger size and much more complex morphology.

We are thus now able to establish the existence and main features of four archaic Vascular Cryptogams from the Rhynie bed. In the present paper additional notes on R. Gwynne-Vaughani are given, and R. major and Hornea Lignieri described in detail. In conclusion, the morphological bearings of the facts will be briefly considered.

Previous to the voyage of the Endurance in 1914–1915, the depth and extent of the Weddell Sea were either based on or surmised from the deep-sea soundings made on the Scotia by Dr Bruce in 1903 and 1904; on Dr Otto Nordenskjöld's ship Antarctic in 1901–1902; and on the German Expedition ship Deutschland under the leadership of Lieut. Filchner in 1912–1913. The first set are confined to the eastern and north-eastern portion, and may be said to run diagonally across the mouth of the sea; the second set were made in the extreme north-western area; whilst those of the Deutschland are disposed right down the centre of the sea, and consist mainly of a south-to-north series approximately along the meridian of 43° W.

This investigation on the morphology of the Fore-brain or Prosencephalon of Elasmobranchii was suggested to me by Professor G. Elliot Smith, F.R.S., and I am indebted to him for introducing me to an interesting if somewhat difficult and perplexing subject. A glance at the literature on the morphology of the prosencephalon will readily convince one of two things—firstly, of the endless field for work in endeavouring to ascertain the true homologies of the neurone areas and fibre tracts in the brain throughout the Phylum Vertebrata; and secondly, of the somewhat unnecessary obstacles which have been introduced into the problem by the more recent additions to a terminology, already overburdened and encumbered, of new terms for equivalent parts. It would appear to be very advantageous if mutual agreement could be arrived at among workers on this subject regarding the use of descriptive terms, and, if such is at present impracticable, that each new worker should refrain as far as possible from applying a new term to a structure already previously described. In one case, namely, that of the tuberculum olfactorium, five different terms have apparently been applied to the same area.

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.

The theoretical determination of the longitudinal seiches of a lake was reduced by Professor Chrystal to the finding of those solutions of the differential equation

which vanish at x = 0 and x = a.

Here x denotes the area of the surface of the lake from one end up to any transverse section, and ranges from 0 to a, a being the total area of the surface of the lake; p(x) denotes the product of the area of the transverse section at x and its breadth at the free surface; λ=σ2/g, σ being the “speed” of the periodic motion and g the acceleration due to gravity; V denotes the total volume of water which has passed the section up to the time t.

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 opportunities for observation were afforded by the voyage and subsequent drift of the S.Y. Endurance. During December 1914 and January 1915 for a period of six weeks she successfully bored her way through pack-ice of every description—drift-ice, open-pack, and very frequently even close-pack. Continually fighting, she penetrated from 59° to 72° S. lat., and finally reached the land water off Coats Land on the latter parallel. As the crow flies, therefore, she was navigated through ice for nearly 800 geographical miles on this voyage; her actual course among the ice-fields and floes was computed to exceed 2000 miles, an achievement without parallel in the Antarctic. The principle adopted was to keep to the east, where presumably there is less pack than in the west; if the Endurance experience is a normal one, however, the meridian of 20° W. long., which was followed, is certainly not far enough east.

Asteroxylon Mackiei was a plant of more complicated organisation and larger size than either Rhynia or Hornea, which have been described from the silicified peat-bed at Rhynie in the two preceding papers of this series. The generic name refers to the stellate outline of the xylem of the stem as seen in cross section, while the specific name commemorates the original discovery of the plant remains by Dr Mackie.

This part of the account of our examination of the plants preserved in the silicified peat-bed of early Old Red Sandstone age found at Rhynie will be devoted to the consideration of a number of general questions concerning the four Vascular Cryptogams which it has yielded.

1. In the first place the morphological characters of Rhynia Gwynne-Vaughani, R. major, Hornea, and Asteroxylon will be reviewed and the attempt made to reconstruct the external appearance of these plants as they grew. In relation to this a few additional features of the plants will be described.

2. This will lead naturally to a consideration of the general bearings upon plant-morphology of the facts mentioned in this series of papers.

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.

In this concluding part of the series of papers on the plants preserved in the Rhynie chert-band, various remains of lower plants that occur in the peat will be described, and some general questions concerning the accumulation and preservation of the deposit considered. The paper is divided naturally into the parts enumerated below.

1. An account will be given of a number of forms of Fungi which are met with in the decayed remains of the vascular plants, and also in the peaty matrix. The fungal remains are so generally distributed that they can be regarded as forming an integral part of the peat. In connection with them, the question as to whether there is evidence of a mycorrhizal relation between any of the Fungi and the Vascular Cryptogams will be considered.