For two centuries and a half the ampullary canal system of Elasmobranch fishes has occupied the attention of a series of investigators, who have treated the subject from a variety of standpoints, and have amassed a considerable literature representing, in spite of repetition and some conflicting statements, a gradual advance to a fuller knowledge regarding the occurrence and the structure of the organs in question.

The systematic study of the cluster of orders lying at the base of the Dicotyledon phylum has of late years become of fundamental importance in view of the various theories advanced by different authorities as to the origin of the so-called Monocotyledons. The anatomical structure of many of these groups has been but little investigated from this aspect, and the present paper is the first of a series which it is hoped to publish with the object of discovering to what extent anatomy supports or contradicts one or other of views held on the phylogeny of flowering plants. One such research is already far advanced, viz. on the anatomy of the Magnoliaceæ, and another, the present contribution, deals with the stem structure of the Papaveraceæ. Although both researches have been retarded owing to one of the authors being engaged on war service, there would seem no reason for delaying the publication of such observations as have been made.

Hitherto there has been described only a single species—Dicoryne conferta (Alder)—amongst the Hydrozoa in which the reproductive body is a sporosac which becomes ciliated and free-swimming. We have found that another species which, as we shall show (pp. 269–271), must be named Dicoryne conybearei gives rise to reproductive bodies of this type, which, however, differ from those of Dicoryne conferta in several important respects. The free-swimming type of sporosac has not been the subject of close observation since 1872; we have therefore made as complete a study of the structure and development of the sporosacs, especially of D. conybearei, as material gathered from several sources would permit.

This Plesiosaur was collected from the Oxford Clay near Peterborough by A.N. Leeds, Esq., F.G.S., and was acquired for the Hunterian Museum, Glasgow University, by Professor J. W. Gregory. The major portion of the skeleton is present, and the bones are in an excellent state of preservation. The specimen has many striking resemblances to Cryptocleidus oxoniensis, but detailed examination showed that it could not belong to that species, and the differences existing in the paddle, shouldergirdle, number of vertebræ, and conditions of ossification are such that it cannot be retained in that genus as now defined. Under the circumstances it seems advisable to create a new genus.

In the year 1810 there appeared in Robert Brown's Prodromus Floræ Novæ Hollandiæ et Insulæ Van Diemen, p. 160, a brief description of a rare Australian Fern to which the generic name Platyzoma was given. The habit of stem and leaf, and in general the form and position of the sporangia, led Brown to the conclusion that Platyzoma was of Gleicheniaceous affinity. It was noted that the plant was heterophyllic; for not only did it possess pinnate leaves suggestive of those of certain Gleichenioid forms, but also small, compressed, and filiform leaves devoid of pinnæ. To the form of the larger and pinnate leaves Brown paid particular attention, noting chiefly that the leaves of Platyzoma were unbranched, whereas a branched condition was typical of the leaves of Gleichenias. This unbranched condition of the leaf seemed to Brown a sufficiently distinctive feature to justify the foundation of a new Gleicheniaceous genus —the monotypic genus Platyzoma; and he named the single species Platyzoma microphyllum.

The expression “architecture” as applied to the leaf was introduced by Prantl in his monograph on the Hymenophyllaceæ. It may be adopted as connoting the sum of the facts of construction of leaves; together with those principles or methods deduced from them, upon which we find the leaf to be built up. The varieties of size, form, and complexity of leaves appear infinite; but similarities in the scheme of their construction are obvious. It cannot be assumed that where similarities occur they are necessarily due to immediate community of descent. They may or may not be. Parallel development under similar conditions may be, and probably has been often, the source of such similarity. But even so it may be possible to connect the simpler and the more complex within the several lines of nearer relationship, and a study of several such lines may be expected to disclose certain underlying principles or methods which have ruled in the construction of foliar organs at large. The recognition of these, in their evolutionary aspect, is the proper basis for a scientific knowledge of leaf-architecture.

In this series of papers it is proposed to describe new or interesting Palæozoic plants, many of which were collected several years ago. Some of these are in the possession of the Geological Surveys of England and Scotland, others belong to personal friends or are in the collections of public museums, while the remainder are in my own collection. They come from various localities and horizons, and a few from coalfields of which papers dealing with their fossil plants have already been published, and they are, in many cases, additions to these lists.

Many of the earlier accounts of the group of Crustacea, known as Isopoda, suffer from want of more detailed diagnoses and figures. To some extent this has been remedied during recent years by the authors of different monographs, but there are still many families which remain somewhat obscure, or only partially understood, owing to the above-mentioned cause. Such a family is the Idoteidæ.

In the present communication I propose to revise the diagnoses of the British genera and species, to set forth in greater detail than has hitherto been done their structure, illustrating the same, and to discuss the classification and affinities of the family as a whole.

The chert of the Muir of Rhynie, containing plant-remains, was discovered by Dr W. Mackie of Elgin while investigating the sedimentary and volcanic rocks of Craigbeg and Ord Hill which occur in that area. The original discovery was made on loose specimens, built into the dykes or scattered over the fields, especially those lying to the north of the road which runs from Rhynie to Cabrach, and east and west of the right-of-way that here connects Windyfield Farm with the public road.

The Psilotaceæ constitute one of the most interesting of existing Pteridophyte groups. This interest is mainly due to their phylogenetic isolation. They are perhaps the most isolated of existing types—showing no close affinity to other Pteridophytes. They are very highly specialised in their anatomy, habit, and habitat, and limited to a comparatively narrow geographical distribution. They include two probably monotypic genera—Tmesipteris and Psilotum—which are closely related. Although both genera are limited to the tropics and sub-tropics, Psilotum has a much wider distribution than Tmesipteris. The latter is confined to the South Sea Islands, Australia, New Zealand, and parts of Polynesia. Up till recent years they have been classed with the Lycopodiales, but this has been more a matter of convenience than an indication of close relationship, and has only served as a temporary classification until more knowledge has been obtained regarding them. The peculiar nature of these plants, as shown in their structure and in their habitat, suggests that they are highly specialised remnants of a much larger group which has practically become extinct. Recent inquiry into the structure of the sporophyte of both plants has made this much more than a suggestion. As a result of the careful investigations of Scott (1908), Boodle (1904), Bower (1894-1908), Ford (1904), and others, there has been a marked tendency to remove the Psilotaceæ from their temporary position among the Lycopodiales and associate them with the extinct Sphenophyllales. Scott (p. 631) states that it seems best to regard the Psilotaceæ as forming a class of their own, the Psilotales, under the main division Sphenopsida—their closest affinity under this class being the Sphenophyllales. This probable affinity of the Psilotaceæ to such an ancient and long extinct race as the Sphenophylls, and the great uncertainty of their relationship to other existing types, have awakened a great interest in these two specialised and isolated genera. When, in addition to this, we consider that the Psilotaceæ is the only group of Pteridophytes in which the gametophyte generation and embryo are not yet definitely known, our interest in these plants becomes twofold, and any new information throwing additional light on their life-histories will be welcomed.