C'est surtout pour étudier le développement post-embryonnaire de la Langouste commune (Palinurus vulgaris Latr.) que je me suis rendu au Laboratoire de Plymouth. L'endroit me semblait excellent parce que la Langouste n'est pas rare près des côtes dans les eaux du Devonshire et de la Cornouaille, parce qu'elle est principalement fréquente sur les fonds rocheux au-dessus desquels se dresse le phare d'Eddystone, aussi enfin, parce que le Laboratoire de Plymouth est très bien installé, avec un bateau, l'Oithona, qui peut se rendre en mer chaque jour et effectuer les pêches les plus diverses.

Durant mon premier séjour au Laboratoire de Biologie maritime de Plymouth, en qualité de “first Ray Lankester Investigator,” j'ai eu la bonne fortune de trouver un certain nombre d'exemplaires de la très curieuse forme larvaire découverte en Ecosse, prés d'Arran, par G. Brook (1889) qui lui donna le nom de trachelifer.

Durant mon séjour au Laboratoire de Biologie maritime de Plymouth, j'ai eu l'occasion d'examiner un lot très important de Pycnogonum littorale, Ström, qui se trouvait dans les collections de l'établissement depuis le 8 juillet 1908. Ce lot ne comprenait pas moins de 3268 individus. Il avait été recueilli au Barbican Pool, vieux port de Plymouth, dans les filets de pêcheurs qui avaient fait leur capture, disaient-ils, à 200 milles O.N.O. des Iles Scilly. Les exemplaires étaient beaucoup plus nombreux, mais le Laboratoire n'avait pas cru devoir en conserver davantage.

Some of the specific and differential characters of these two species have already been enumerated by Pace (1). Subsequently Norman (2) denied that these two forms were different, so that the literature on them was left in an unsatisfactory state. On investigating these two forms, however, I have obtained sufficient evidence-from the characters of the gonadial tubes, the calcareous collars, and the young of both forms-to verify the observations of Pace and to meet satisfactorily the objections put forward by Norman against them. The differential characters of these two species as given by Pace (loc. cit.) have been verified in an unpublished investigation by Mr. W. De Morgan and by the present writer.

On August 14th, 1913, a fine male specimen of Anthura gracilis was taken by the Oithona, in the young-fish trawl working at the surface at night, about six miles west of the Eddystone.

In February of this year Mr. J. H. Orton collected a number of small nereids on the piles of a wharf at the Great Western Docks at Millbay, Plymouth. These he kindly handed over to me for identification, and, along with other material collected at Plymouth in March, they form the basis of this paper.

These nereids proved to be none other than the little-known Leptonereis glauca of Claparède, of which the only specimen hitherto recorded from the shores of this country was found by Major E. V. Elwes at Oddicombe (8, p. 351) some years ago.

While on shore-collecting expeditions in this district it was frequently observed that Echinus miliaris has the habit of associating together in pairs, and sometimes in groups of more than two. The association of these pairs and groups is sometimes so intimate that it is not possible to interpose even the blade of a penknife between the interlocking spines of the urchins. In all cases observed except one, such pairs were placed side by side, but in one particular case the apical region of one individual was almost certainly placed adjacent to the apical portion of the other. In all the collecting expeditions—made at various times of the year between April and August—on which groups were collected, the total number of urchins of all sizes obtained amounts to about 710. Among this number were obtained 84 groups, which amount in all to 189 specimens. In the earlier part of the investigation a group was taken as such if the members were merely fairly close together, but afterwards only those specimens were recorded which were actually touching one another in the manner described above. Out of the total of 84 groups only 27 were actually recorded definitely as touching one another, although some of the other groups may have been touching. Of these 27 closely associated forms all the individuals were ripe except 3 small specimens belonging to two pairs which were recorded as having an immature gonad. The remainder consisted of 19 pairs, 2 pairs, 1 pair, and 3 groups respectively.

In July, 1912, a paper was published in the Proceedings of the Royal Irish Academy (Vol. XXXI) on the Marine Porifera of Clare Island, by Miss Jane Stephens, in which the authoress gives an excellent account of a new species of Calcareous Sponge, Leucandra cliarensis. In April of the same year I happened to be working at the Marine Laboratory at Plymouth, and my friend Mr. Orton brought me several specimens of a very pretty little calcareous sponge just collected by him at Wembury Bay. I was too much occupied with other work to examine these carefully at the time, but simply preserved them in spirit. Recently I have examined them in detail, and find, curiously enough, that they belong to the species described by Miss Stephens from Clare Island on the west coast of Ireland.

Confusion has reigned in the works of British authors as to the relationship between Plumularia catharina, Johns., and a more simple form, with unbranched stem, found, like the former, on many parts of the coast. Johnston and Hincks, and the majority of their successors, have recorded the simple form, where it was thought worthy of mention, as a “stemless variety” of the former; but examination of the type specimens of P. catharina in the British Museum has proved that a fundamental distinction exists between the two forms. P. catharina is a branched species and bears on each side of a hydrotheca a pair of lateral sarcothecce; the other is a branchless, bristle-like form, bears on each side of a hydrotheca a single lateral sarcotheca, and has been long known as Antenella (or Plumularia) secundaria (Gmelin).

In the year 1755 Ellis described in his “Natural History of the Corallines,” as “Alcyonium pulmonis instar lobatum,” a “sea production” from Whitstable, which the fishermen there had brought to him under the name of “Sea-Fig.” As regards the systematic position of this form, he expresses himself only in so far as to place it with the Alcyonians, a group in which were united at that time, along with true species of Alcyonium, Ascidians, Hydroids, Sponges and even Algæ. As a doubtful synonym of his species Ellis put forward the Pulmo marinus of Rondelet (1555), which however has nothing whatever to do with it and indeed cannot be certainly determined. During the following years, Ellis' work was translated into several languages. A Dutch and a French translation, both dating from the year 1756, are known to me, the former by Tak, the latter by Allamand. There is also a German translation by Krüniz dated 1767.

The results of the writer's investigations on the ciliary mechanisms on the gills of Mollusca and Amphioxus (1 and 2) gave rise to the suggestion that similar mechanisms might probably also occur in Brachiopods, for it is a well-known fact that Brachiopods—like some Molluscs and Amphioxus—feed on the smaller organisms which are to be found floating in the sea. Owing to the kindness of Dr. H. C. Williamson, of Aberdeen, I have been able to examine living Crania which were obtained by dredging in Loch Fyne, and living Terebratula have also been obtained from Naples. An investigation of the living gill-filaments—or lophophoral cirri, as they are frequently termed in this group—showed that the ciliary mechanisms on these filaments are essentially the same as those occurring on the gill-filaments of Amphioxus, Lamellibranchs, some Gastropods, and most Ascidians. As it was found that existing accounts of the mode of feeding in Brachiopods are vague and incomplete the following description of the process has been written.

An investigation of the rate of growth in Marine Invertebrates was begun in 1911, and a large amount of material the age of which is known has now been collected from various sources. The particular objects of this research are: (1) to establish the age of common marine invertebrates, (2) to determine the minimum age at which these forms begin to breed, (3) to examine the rate of growth at different seasons of the year and under different conditions, (4) to investigate the fecundity of different forms so far as possible, and (5) to collect the scattered literature on these subjects.

The material on which the present report is based was collected by the Oithona from 1906 to 1909 inclusive, and during the latter half of 1913. Attention was directed particularly to the capture and determination of the post-larval fishes. The investigations during the first four years were carried out by Mr. A. E. Hefford, and his notes have been fully relied upon for the identification of the species. For the collecting and working out of the 1913 material I am directly and wholly responsible.