Observations on breeding (1, 1914; 2, 3, 1920) and experiments on the rate of growth of marine invertebrates (4, 1914; 5 to 9) have been carried out since 1911 (excepting the war period).

Mr. Leigh-Sharpe, in his account of the external structure of this interesting Copepod (1926), concludes that it is most nearly related to the Ascomyzontidæ. Having recently obtained a number of larvæ, hatched from adults obtained at Plymouth, and finding that my own conclusion as to the relationship of the genus differs from that of Mr. Leigh-Sharpe, it seems worth while to describe the larvæ and the bearing they seem to have upon the systematic position of the adult.

The larvæ hatch and become active inside the egg-sac. Immediately after becoming free they swim vigorously for a short time, but very soon sink to the bottom and remain quiescent, with occasional spasms of activity.

During a short stay at the Laboratory at Plymouth, with the object of studying the larvæ of Longipedia and Misophria, I was successful in identifying the nauplius of the former, and, as it is of rather exceptional interest from the systematic point of view, the various stages are described here. I did not find the adult of any species of Longipedia and am not able to describe the first nauplius with certainty, but the identity of the series as a whole was settled beyond doubt by the moulting of a late nauplius into a Copepodid which could be definitely identified as a species of Longipedia. It is impossible to say to which species it belonged, but the specific determination is not of serious importance.

That a mother worm protects its eggs until tie young are hatched is common enough among Polychætes, but not in the family Phyllodocidas.

McIntosh (1908) mentioned in his British Annelids, Vol. II, Pt. I, p. 49, that two female specimens of Notophyllum foliosum, procured by his late friend Dr. Howden, at Lamlash, Arran, in August, were laden with mature eggs. Certainly the words “were laden” used here tell us something about the particular habit of the worm, but the sentence is too short and is not emphatic enough to attract attention.

The facts of Polychæte embryology inform us that the change of the trochonphore into the perfect worm consists, first of all, in a growing out of the posterior section of its body and a gradual reduction of the anterior part, segmentation appearing at the same time. Thïs phenomenon depends upon a marked change of the mesodermal bands, situated on each side of the intestine. Each of them is separated into two cell-layers, which spread out toward the mid-ventral and mid-dorsal lines. Then a segmentation makes its appearance in them, proceeding from in front backwards, and almost simultaneously the two layers of the bands separate from each other, by the formation of a cavity in each section or segment. That new segments are gradually formed one after the other, and from before backwards, in the hinder part of the growing body, holds true universally, but, at the extreme end a segment has been individualised from the first, or at a very early phase of the segmentation, and this segment does not divide again even to the end of development. In this way the pygidium is formed, and it represents the posterior individual portion of the trochophore. The growth of Polychæte-larvæ is therefore anteanal and entirely in the penultimate segment.

During a short visit to Plymouth, in 1928, Dr. M. W. de Laubenfels made a collection of sponges which, with the exception of six, he identified and deposited in the Biological Laboratory at Plymouth. Before leaving England he left these six with me, with the request that they should be identified. This I have now done, and the results have proved extremely interesting, adding six species, Halichondria bowerbanki, Mycale similaris, Iophon hyndmani, Endectyon delaubenfelsi, Hymedesmia stephensi, and Pachaxinella subdola, to the recorded faunal list for Plymouth, of which three are new species.

Accounts have been given in previous papers (1925, 1926, 1928) of measurements of submarine illumination carried out near Plymouth by means of photo-electric cells. A further paper (1929, 3) recorded the results so obtained during 1928. An account is now given of photo-chemical measurements made in that year, simultaneously with the photo-electric measurements.

Brandt (1927) has summarised and reviewed our knowledge of the nitrogen compounds existing in sea-water, including nitrites. In general, estimations of nitrite in sea-water have been made colorimetrically, using the Griess-Ilosvay reagent, which has also been used in the present work. Usually the amount of nitrite found, recorded as milligrams of nitrogen per cubic metre, was small. Raben's results have been grouped by Brandt as follows, 0 mg., 48 cases; under 1 mg., 53 cases; 1–4 mg., 21 cases; 5–9 mg., 6 cases. Orr (1926) in the Clyde Area, found from under 1 mg. to about 10 mg. in June 1925, the deeper water having more than the upper layers. Harvey (1926) states that, “in a number of. water samples from the English Channel, examined either on board ship or immediately after landing, no definitely detectable traces of nitrites could be found either by the Griess-Ilosvay reagent or with the strychnine reagent without sulphuric acid, except in the case of inshore water subject to pollution. After storage-an appreciable quantity of nitrite has been detected in several instances. In water from 830 metres in the Bay of Biscay, preserved with mercuric chloride when collected, and in water at various depths up to 3000 metres, similarly preserved, collected by the R.R.S. Discovery some 200 miles west of Portugal, no nitrite could be definitely detected.”

This apparatus was assembled at Millport for the electrometric titration of solutions which, being highly coloured, cannot well be titrated with an indicator. It may be used also for highly dilute solutions, unless they are so slightly buffered that their pH value is appreciably changed by the addition of a small quantity of quinhydrone. Measurement of hydrogen-ion concentrations at the quinhydrone electrode has also been attempted with the apparatus. The apparatus is suitable for use at sea.

The object in publishing these notes on the Spur-Dog, Acanthias vulgaris Risso, is to show the close resemblance, in the distribution of the sizes and sexes, between this fish and the Hake. The Hake will be dealt with in a future paper.

The work has been done during voyages in which the Hake has been the principal object of research. The data on Dogfish have therefore been collected at odd times during a very busy programme on the Hake, and this must be my apology for inadequacy or discontinuity in the figures presented. I would especially thank my colleague, Mr. W. Johnston, and my friend, Mr. C. E. D. Enoch, for their willing help in this entirely unofficial work; and Mr. J. Armitage Robertson for his help in the arrangement of the text.

There seems to be some uncertainty about the exact stage at which the horny case is secreted around the fertilised Elasmobranch egg. Those textbooks which have been consulted either pass over the matter in silence or give the impression that the shell is secreted while the egg is passing through the nidamental organ. Sedgwick (1905), for example, says (p. 143): “The shell is formed round the ovum and its albumen in the lower dilated part of the oviduct, but the material of which it is composed is secreted by the oviducal gland.” Of late years the question seems to have received little attention, but there are several papers on the subject published twenty or more years ago.

This paper is a continuation of Part I in a strict sense, and deals with the methods and samples considered previously. More prolonged immersion tests have enabled a more accurate estimate to be reached as to the relative values of the methods of preservation. One new preservative has been tried, an oily substance sold as “Neo-Russigen,” a sample of which was supplied by the Ministry of Fisheries; in the absence of any chemical analysis of this there is no guarantee that subsequent supplies will approximate to the sample received, to which alone must the data presented be considered to apply.

This instrument was designed for taking marine muds for analysis. The requirements were that it should raise a column of mud, from eight to sixteen inches long, and without appreciable disturbance, or contamination with metal. An instrument working on the same principle was used here by Mr. R. Macdonald, and was made in Oslo. The advantages of the present model are that, while small enough to be worked by hand, it is capable of taking larger samples, and from bottoms of very varying consistencies.

The Clyde Sea Area is in many ways an ideal ground for the investigation of the nutrient salts in the bottom deposits. The different lochs present a range of depth of water of from 0 to 200 metres: some parts have strong tidal currents up to five knots, while others are practically unaffected by the tide: some lochs have also been affected by the dumping of sewage and harbour sludge, and the effect of these can be examined. Conditions may also be compared in muds ranging from the loch heads to the almost open sea conditions at Ailsa Craig.

The following investigations were carried out in order to test the validity of the oft-recurring statement to the effect that “burrowing organisms live under fresh-water conditions during low tide in estuaries.” This type of statement is usually made in respect to organisms which live in the sand or mud of estuaries in which, at low tide, a stream of fresh, water passes over the ground in which the organisms are buried.

I have not been able to find any references to show that work has ever been done on this subject with the idea of determining the actual salinity of the water held by such sand. Therefore I carried out the following experiments to try to find if data could be procured which would be sufficiently consistent to lead to any conclusions.

The present paper continues the account of my experiments ou the capacity of fishes to form conditioned responses towards definite stimuli under strict experimental control. No change has been made in the method of recording the results except in the section on auditory discrimination in the wrasse. This slight variation is explained in the appropriate place.

All the experiments described in this part belong to Section A of the previous paper (1), in which food is the unconditioned stimulus. The work which has been carried out in Section B will receive fuller treatment at a later date.

In continuation of the study of the vertical distribution of the pelagic young of Teleostean fishes, already reported on for 1924 and 1925 (1), a further fifteen stations were made with the two-metre stramin net in the daytime between April and September in 1926. The collections were made in a manner exactly similar to that for those of the previous years, hauls of ten minutes' duration being made almost always at six different depths with the net towed horizontally as near as possible at the same speed on each occasion. The Admiralty depth-recording instrument was used at every station, and the results for each haul are given in Figures 6 and 7 on pages 666 and 667, which show the graphic records of the path of the net through the water for each haul. (That for June 25th is not included, an unsatisfactory record being obtained on that day owing to the drum of the recorder not having been fully screwed down, see 4, p. 431.)