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TTeherty fat thi4i owt t 2 Srararent , Creer ay saath, sig jot Soestis y oe re a bye sentatit 3H Avera he 4 bp a themehetada ate ate psdned v) aaseheaer tet cakes fi hed oad Pres ed vos fib e, Ma SARS ere hak ans pti uu Wekiedobese sets Ye welet rie Sore aregese repeats ie) ie err: whan shoves be 4 iy es riggers vin tet rregute i He a be abit epee oe sb eg th syle yoaene ve peeesenteniien Ly aiase shad SEAR AG bss atin iitd fhe Pity 4 dE BEA dt Lert aoe ag teed iiar nthe Me A pegnes si pt = rer? soy iH a eheer ihe : eae th Fi plow Nae sabaek i aa esesne 194 meri rit f ea onars eat the seg 6rd PP ieee a pvt code ty 44 i sentation 44 tate bd 94 aie se Heeaiba reuse Fai dh he Ablehete do ate br wanett dats aby, Lew HDPE ty ay ; ELEM ad 24 rhs dmg sgse ate cate ipa it serie bbibed nia6 tang Satis aie por ae qyete phlgs ahd i ved tthe "9 diy pry ep ey Mae er dody sora seta weartegety Md th ranyyye ey vate abs va teed resis) mriahy epi Red bes hiea i rendre Le nth Theoteo ies Me haha Ap nde tipi epvherte atin ghia h en Abba g etic phehed Ad prarenrel Hoss! pleas adh oe eS 14; 24 Journal OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM. VOT, UMA 3a ONS.) 1916-18. 4G i PILYMO UW IE - PUBLISHED BY THE ASSOCIATION, The Council of the Marine Biological Association wish it to be understood that they do not accept responsibility for the accuracy of statements published in this Journal, excepting when those statements are contained in an official report of the Council. ERRATA. Page 14, line 2. For “1-20 mm.” read “1-4 mm.” Pages 240-241, Tables XXXVI and XXXVII. The records in these two tables should be added to those of Table XX XV as Gobius sp. Page 289. In the second square of the last row of the square diagram for GG, went» e” read “C. Page 291, line 3. Insert the word ‘“ coloured ” before the word “ offspring.” ' » 13. For ‘all black offspring” read “no red offspring.” Page 317, line 6. For “36-6” read 32-6." For “12:2” read “WG-30 CONTENTS OF VOLUME XI. (NEW SERIES.) List of Governors, Founders, and Members— May, 1917 . Report of the Council— 1915 1916 1917 Balance Sheet, 1915 ditto 1916 ditto 1917 Aten, E. J. Post-Larval Teleosteans collected near Plymouth during the Summer of 1914 5 . Heredity in Plants, Animals, and Man Food from the Sea é : s The Age of Fishes and the Rate at which they Grow ALLEN, E. J., AND Sexton, E. W. The Loss of the Eye-pigment in Gammarus chevreuai. A Mendelian Study Curter, D. Warp. A Preliminary Account of the Production of Annual Rings in the Seales of Plaice and Flounders FLATTELY, F. W. Notes on the Geology of Cirratulus (Audouinia) tentaculatus (Montagu) . Krys, J. A. A List of Maritime, Sub-Maritime, and Coast-frequenting Coleoptera of South Devon and South Cornwall, with especial reference to the Plymouth District Lesour, Martie V. Stages 1m the Life History of Calanus finmarchicus (Gunnerus) Experi- mentally reared by Mr. L. R. Crawshay in the Plymouth Laboratory Notes on the Life History of Anuphia petioluta (Kroyer) Medusze as Hosts for Larval Trematodes . é : 5 The Microplankton of Plymouth Sound from the Region beyond the Breakwater : : ; : : The Peridiniales of Plymouth Sound from the Region beyond the 3reak water 470 60 497 1V CONTENTS OF VOLUME XI. Lepour, Marte V. (continued). PAGE Some Parasites of Sagitta bipunctata : : i : . 201 The Food of Post-Larval Fish . : : ; : . 433 A Trematode Larva from Buccinum undatum and Notes on Trematodes from Post-Larval Fish 3 ; ‘ : : :. “olla Marruews, Donap J. On the Amount of Phosphorie Acid in the Sea-water off Plymouth Sound 122, 251 Orton, J. H. An Account of the Researches on Races of Herrings carried out by the Marine Biological Association at Plymouth, 1914-15. : .. val Sexton, E. W., anp Wine, M. B. Experiments on the Mendelian Inheritance of Eye-colour in the Amphipod Gammarus chevreuxt : . c : v ORS See also ALLEN, E. J., and Sexton, E. W. Abstract of Memoir recording Work done at the Plymouth Laboratory— The Development of Aleyoniwm digitatum, with some Notes on the Early Colony Formation. By Annie Matthews F : : . 258 In Memoriam: H.C. Dannevig . ; : ; ; pe lit Stages in the Life History of Ca/anus finmarchicus (Gunnerus), Experimentally Reared by Mr. L. R. Crawshay in the Plymouth Laboratory. By Marie V. Lebour, M.Sc., Assistant Lecturer in Zoology, Leeds University. Temporary Naturalist in the Plymouth Laboratory. With Plates 1 to 5 in the Text. [The stages in the development of Calanus finmarchicus described and figured by Miss Lebour in the present paper were taken from culture jars given into my charge by Mr. L. R. Crawshay, when he left the Laboratory to undertake military duties in connection with the war. In one jar at that time the first copepodid stage, from eggs laid in the jar, had just been reached, and the technical details for the successful rearing of the animals had been mastered. The experiments had been conducted with great care, and all possible precautions had been taken to prevent con- tamination. Subsequently the experiments were repeated up to a certain point by myself and some additional stages obtained to complete the series. The cultures were made in 2-litre glass beakers, containing “ outside ”’ sea-water filtered through a Berkefeld filter. In order to secure an even temperature the beakers stood in the circulating water of the Laboratory tanks, and a pure culture of the diatom Nitzschia closterium was used as food.—KE. J. ALLEN. | Aut the 5 copepodid stages (the 6th being the fully formed copepod) and 5 out of the 6 nauplius stages were found. Unfortunately the 6th nauplius stage was missed and could not be found in the material, but it is described and well figured by Grobben (1903), and his figures and description show that it is very like the same stage of Pseudocalanus and Paracalanus described by Oberg (1906). The latter author’s descrip- tions agree very closely with all the corresponding stages of Calanus jinmarchicus, the size in all cases being the chief difference. In the very NEW SERIES,—VOL. XI. NO. 1. MARCH, 1916. A 2 MARIE V. LEBOUR. young nauplius stage the feelers differ in being long and thin in Calanus finmarchicus and short and hook-like in Pseudocalanus elongatus. Nauplius Stage III is much the commonest stage and occurred all the time the material was being examined. The animal probably stays some time in this stage. The number of bristles on the antennules of the nauplius is a sure guide to the stage, as they are constant and very easily seen. They also agree exactly in number with similar stages in Pseudocalanus and Para- calanus. The colouring was much the same throughout all the stages, although not so marked in the early nauphus. The first nauplius stage has pigment present only in the region of the alimentary canal, where a few orange and red spots occur, and the tips of the appendages are a light orange. Later on the colouring is more marked. In the first copepodid stages and after the antennules are beautifully spotted with dark red, the bristles being red, and the furcal bristles are red merging into orange ; the tips of the antenne and mandibles are red, and the distal portions of all the appen- dages as far as the maxilhpeds and also the hind end of the body are yellow. This colouring appears in all the copepodid stages with slight variations. Grobben’s descriptions agree well with the present material. Those stages which he figures are probably I, III, IV or V, and VI, also the first copepodid stage. THE NAUPLIUS. Stace I (Plate 1, Fig. 1). Only one specimen. This is very lke Grobben’s figure of the early nauplius, but he figures only 2 bristles on the antennule where the present specimen has 3. It appears to be an earlier stage than any of Oberg’s. His Stage I of Pseudocalanus agrees with Stage II of the present species. His Stages III—V agree with the corre- sponding stages of Calanus as described in the present paper. Length of body 0-21 mm., oval, slightly more pointed posteriorly than anteriorly, faintly pik with orange tips to the appendages. Eye dark red. A pair of thin feelers at the hind end of the body. Appendage I. ANTENNULE (Plate 2, Fig. 1). The end segment divided off, the other 2 merely indicated. A small bristle just behind the end segment, the latter bearing 3 bristles. Appendage II. Anrenwna (Plate 2, Fig. 6). Coxopodite with a large thorn-like masticatory process. Basivpodite with 2 roundish prominences, the proximal portion with 2 small bristles. M. V. Lepour. CALANUS FINMARCHICUS. Prarn 1. Ah M.V.L. pet. [3 ] 4 MARIE V. LEBOUR. Endopodite with 2 long bristles at the end. Exopodite with 6 segments, the 7th showing under the skin, Ist segment short with no bristle, 2—5 with one bristle each, 6 with 2 bristles. Appendage III. Manpis.e (Plate 2, Fig. 11). Coxopodite with a small bristle. Basipodite with a large blade and 2 small bristles. Endopodite with 2 segments indicated, Ist with 2 small bristles and a third showing under the skin ; the end segment with 2 long bristles. Exopodite with 4 imperfect segments, 1-3 with one bristle each, 4 with one long and one short bristle. Stace II (Plate 1, Fig. 2). Two specimens. Length of body 0-27 mm., oval, transparent, the same colouring as in I. Hind feelers longer than in I, body bent slightly dorso-ventrally. Appendage I. ANTENNULE (Plate 2, Fig. 2) with 3 segments, the Ist with no bristle, the 2nd imperfectly divided into 3, each portion with a small bristle; the end segment with 3 long bristles and an accessory bristle ; a group of minute spies dorsally. Appendage II. Antenna (Plate 2, Fig. 7). Coxopodite with a large thorn-like masticatory process and a small bristle. Basipodite with a masticatory process and 2 lobes each with a small bristle. Endopodite with a pair of small bristles and at the end 3 long bristles. Exopodite with 7 segments, 1st short with no bristle, 2-6 with one bristle each, 7 with 2 bristles. Appendage III. Manpisie (Plate 2, Fig. 12). Coxopodite with a small bristle. Basipodite with a large blade. Endopodite with 2 segments indicated, Ist with 3 small bristles, 2 with 2 small bristles, and 3 long bristles at the end. Ezxopodite with 4 segments indicated, 1-3 with one bristle each, 4 with 2 bristles. Stace III (Plate 1, Fig. 3). Several specimens. Length of body 0-42 mm., the hind end well marked off from the front, body much flexed dorso-ventrally, transparent, coloured rather more strongly than in the first two stages. Hind end of body armed with 2 long feelers, one dorsal and one ventral, a pair of lateral and a pair of posterior hooks. Near the hooks are 3 rows of very short, sharp spines and the same sort of spines surround the bases of the hooks. Besides the 3 pairs of appen- dages there is a slight indication of a 4th (maxillule). M. V. Lepour. CALANUS FINMARCHICUS. : PHATE 2) M.Y.L. DEt. 6 MARIE V. LEBOUR. Appendage I. ANTENNULE (Plate 2, Fig. 3). With 3 segments, no bristle on the first segment, second imperfectly divided into 3, each with a bristle, the end segment with 2 small bristles dorsally, one ventrally, and 3 long bristles and an accessory bristle at the end. The group of small hooks are present dorsally as in II. Appendage II. Anrenna (Plate 2, Fig. 8). Coxopodite with 2 large masticatory processes and a small bristle. Basipodite with 2 imperfectly divided segments, the proximal with a long, straight masticatory process and 2 small bristles, the distal with one small bristle. Endopodite with 2 imperfectly divided segments, the proximal with 3 small bristles, one smaller than the others, the distal with 3 large and one accessory bristle at the end. Exopodite with 7 segments, the Ist with no bristle, 2 with one large and one small bristle, 3-5 with one bristle each, 6-7 with 2 bristles each. Appendage III. Manprste (Plate 3, Fig. 1). Coxopodite with a large process and a small bristle. Basvpodite with a broad blade and 2 small bristles. Endopodite with 2 imperfectly divided segments, the proximal with 2 pairs of bristles and a masticatory process, the distal with 2 pairs of small bristles and 2 long end bristles. Exopodite with 4 segments, lst with 2 bristles, 2-3 with one bristle each, 4 with 2 bristles. The 4th appendage is very feebly represented by a faint prominence behind the mandible. Stace IV (Plate 1, Fig. 4). 2 specimens. Length of body 0-48 mm. The same shape and colouring as III. Hind end of the body armed with 2 long feelers, 3 pairs of lateral hooks, one pair of end hooks, and 2 pairs of ventral hooks. Small hooks as in III. Appendage I. ANTENNULE (Plate 2, Fig. 4). With 3 segments. No bristle on the Ist segment, 2 incompletely divided into 3 each with a bristle, terminal segment with 3 ventral bristles, 4 dorsal bristles, and 3 long bristles and an accessory bristle at the end. Small dorsal hooks as in IT and ITI. Appendage II. AnrEnna (Plate 2, Fig. 9). Coxopodite, basipodite and endopodite as in III. Exopodite with 7 segments, 1st with no bristle, 2 with 3 bristles, 3-7 with one bristle each, 7 with 3 bristles. Appendage III. Manprsue (Plate 3, Fig. 2). Coxopodite with a well-developed toothed process like the adult but with fewer teeth. M. V. Legour. CALANUS FINMARCHICUS. PATE) Se cae 8 MARIE V. LEBOUR. Basipodite with a large blade and 3 small bristles. Endopodite with 2 lobes, the inner lobe with 4 bristles and a small masticatory process, the outer lobe with 6 bristles. Exopodite with 4 segments, the Ist with one large and one small bristle, 2-3 with one bristle each, 3 with 2 bristles. Appendage IV. MaxiLuu Le (Plate 3, Fig. 4) small with 2 lobes. Endopodite with 4 small bristles. : Exopodite with 3 small bristles. Stace V (Plate 1, Fig. 5). This specimen, the only one of its kind found, was unfortunately dead and damaged. Length of body 0-51 mm. Much like Stage IV. The hind part of the body divided into 2 segments with indications of a third, and besides Appendage IV there are traces of V and VI, which show as minute knobs. The armature of the hind end was damaged, but 3 pairs of lateral hooks could be seen, so that there are almost certainly 2 end feelers, a pair of end hooks and 2 pairs of ventral hooks, corresponding to the same stage in Pseudocalanus. Appendage I. ANTENNULE (Plate 2, Fig. 5) with 3 segments, the Ist with no bristle, 2 imperfectly divided into 3 each. with a bristle, the terminal segment with one proximal and 2 distal bristles on the ventral border, 6 bristles and a group of small hooks on the dorsal border, and 3 long bristles and an accessory bristle at the end. A row of minute hooks occur inside the tip of the terminal segment. Appendage II. AnrrEnna (Plate 2, Fig. 10). Coxopodite and basipodite as in III and IV. Endopodite as in IV, but with 4 bristles on the inner side and 5 end bristles. Exopodite as in IV. Appendage III. Manpisue (Plate 3, Fig. 3). Coxopodite as in LV. Basipodite with one strong and 4 small bristles. Endopodite, the inner segment with 2 pairs of bristles and a masticatory bristle, the outer segment with 2 pairs of bristles and 2 long end bristles. Ezxopodite as in IV. Appendage IV. MaxiLiute (Plate 3, Fig. 5). Not well seen, as it was somewhat injured. Basvpodite with 2 small bristles. Endopodite with 6 small bristles and 2 long end bristles. Exopodite with 2 short bristles and 3 long end bristles. ‘Stace VI. Not seen. Grobben gives a good figure of this stage, which is very like the description and figure of Pseudocalanus by Oberg. The STAGES IN THE LIFE HISTORY OF CALANUS FINMARCHICUS. 9 rather long body is armed at the hind end with 4 pairs of lateral hooks, 2 feelers, 2 end hooks, and 2 pairs of ventral hooks. The maxille and maxillipeds are well developed and swimming feet I and II are present as bilobed structures. This is the last nauplius stage. COPEPODID STAGES. There are 5 copepodid stages before the animal is fully formed. These were recognised by Gran (1902), who gives 6 stages, the last being the mature Calanus. All the 5 stages occurred and were taken from ex- perimental jars started on March 30th, 1915. Naupln first appeared between the 17th and 24th of April, and on May 19th Stage V was taken from the jar, having taken certainly less than two months to grow from the egg to this stage. The species can be recognised from the first copepodid stage by the 2 long sensory bristles on the penultimate segments of the antennules. The rostral processes are distinct even in the first stage, which, according to Oberg, is not the case with Pseudocalanus, where they appear only in the second stage. Stace I (Plate 1, Fig. 6, and Plate 4, Fig. 1). Length of body 0°80 mm. Three free thoracic segments and urosome of one segment with an anterior constriction. In shape like the adult, but broader in comparison with its length. Caudal furca like the adult, but with 3 long bristles and one short bristle, besides a short inner bristle each side. The antennules are now long hke the adult, and usually held out almost at right angles to the body. Colour pale yellow all round the edges of the body, antennules, antenne, mandibles, part of maxillule, maxilliped, and caudal furca, the tips of all these appendages changing from yellow to red as the extremities are reached. Red pigment occurs all along the antennules, the 3 end segments being almost completely red, and dark red blotches run from the base to about the centre. Traces of red pigment are to be seen in the anterior part of the body. Eye dark red. Rostral processes present. There are 2 pairs of well-developed swimming feet and one rudimentary pair. All the other appendages are well developed. Appendage I. ANTENNULE 10 jointed, long, red sensory bristles, one on the antepenultimate and one on the penultimate segment. Appendage II. Anrenna (Plate 3, Fig. 6). Coxopodite very small with one bristle. Basipodite, the masticatory bristle has disappeared. 2 bristles present. M. V. Lepour. CALANUS FINMARCHICUS. PLATE 4. M.V.L. DEL. [10 ] V. LEBOUR. M.V.L. DEL. [ 11 ] 12 MARIE V. LEBOUR. Endopodite with 2 segments, Ist with 2 bristles, 2 with 4 lateral bristles and 5 end bristles. Exopodite with 7 segments, 7th as long as the 2nd, 1st with one bristle, 2 with 3, 4-6 with one each, 7 with 3 and one very small bristle. The antenna is now very like the adult, except for the number of bristles on the endopodite, the full number not yet being formed. Appendage III. Manprete (Plate 3, Fig. 7). Coxopodite with a conspicuous toothed process. Basvpodite with 4 very weak bristles. Endopodite with 4 bristles on the proximal portion, 6 bristles at the end. Exopodite with 5 segments, 1-4 with one bristle, 5 with 2 bristles. Much like the adult mandible, but without the full number of bristles on the endopodite. Appendage IV. MAxILLute (Plate 3, Fig. 8). Coxopodite with a large lobe, the gnathobase, armed with 6 spiky eating bristles. Basipodite with 3 lobes, 2 lobes on its inner margin each with 2 short bristles, and a large lobe on its outer margin, the epipodite, armed with 3 long and stout bristles with red tips. Between the epipodite and the exopodite is a very small lobe with a small bristle. Endopodite, the proximal lobe with 3 bristles, the end lobe divided into 4 portions, lst with 2 bristles, 2 with 2, 3 with 3, and 4 with 2 bristles. Exopodite with 7 bristles. This has all the parts of the adult maxillule, but not the full number of bristles on the basipodite, endopodite, and exopodite. Appendage V. Maxiita (Plate 3, Fig. 9). Coxopodite with 4 segments, 1st with 3 long and one short bristle, 2-4 with 2 long and one short bristle. Basipodite with 2 long and one short bristle. Endopodite with 3 segments, Ist with one long bristle, 2-3 with 2 long and one short bristle each. Now the same as the adult maxilla. Appendage VI. Maxinuipep (Plate 3, Fig. 10). Coxopodite of 3 parts, Ist with one bristle, the other 2 witlt 2 short bristles each. Basipodite with 2 short and one very short bristle. Endopodite with 2 segments, 1st with one bristle, 2nd with 4 bristles. Appendage VII. 1st Swimurne Foor. Coxopodite and basipodite with no bristles. STAGES IN THE LIFE HISTORY OF CALANUS FINMARCHICUS. ils; Endopodite unsegmented, with 4 long bristles. Exopodite unsegmented, with 4 thorns on the outer margin, a terminal blade, and 3 bristles inside. Appendage VIII. 2np Swimmine Foor. Like the first, but with one more bristle on the inside of the endopodite. The exopodite has 4 thorns outside and a terminal bristle, with 3 bristles inside. Appendage IX. 3rpD Swimmine Foot with 2 lobes, each lobe with 2 hooks at the end. Stace II (Plate 4, Figs. 2 and 6). Length of body 1:20 mm., 4 free thoracic segments, urosome of 2 segments. Caudal furea like the adult, with 5 bristles and a small lateral inner bristle. Colouring the same as I, but slightly lighter. 3 pairs of swimming feet and the rudiments of a 4th pair. Appendage I. ANTENNULE with 12 segments, the last 7 the same as I. Appendage II. AnreNnNaA the same as I. Appendage III. Manprse the same as I. Appendage IV. MaxiILuute the same as I, but with 7 bristles on the epipodite. Appendage V. Maxriia the same as I. Appendage VI. Maxiturrep (Plate 5, Fig. 1). Endopodite with a 3rd segment, Ist segment with one broad and 2 small bristles, other segments as in I. Appendage VII. 1st Swimmine Foor (Plate 5, Fig. 2). Endopodite with 2 segments, no bristle on Ist segment, 2 with 2 long bristles on the outside, one terminal bristle, and 4 bristles inside. Ezxopodite with 2 segments, a thorn on the outside of the first, 2 thorns on the outside of the 2nd, a terminal blade, and 4 long bristles inside. Appendage VIII. 2np Swimine Foor (Plate 5, Fig. 3). Endopodite with 2 segments, Ist with one bristle, 2nd with 4 bristles inside, a terminal bristle, and 2 bristles outside. Kxopodite with 2 segments, 1st with a thorn, 2nd with 3 thorns outside, a terminal blade, and 4 bristles inside. Appendage [X. 3RD SwimMinG Foor (Plate 5, Fig. 4). Endopodite unsegmented, one proximal and 3 distal bristles inside, a terminal bristle, and one bristle outside. Ezopodite unsegmented, 3 thorns outside, a terminal blade, and 3 bristles inside. Appendage X. 4TH SwimmineG Foor with 2 lobes each with 2 hooks. 14 MARIE V. LEBOUR. Srace III (Plate 4, Figs. 3 and 7). Like Stage II in colouring. Body more elongated. Length 1-20 mm., 5 free thoracic segments. Urosome of 2 segments. All 5 swimming feet present, the 5th rudimentary. Appendage I. ANTENNULE with 16 segments, otherwise like II. Appendage II. Antenna like I and II, but with 6 bristles on the inner part of the endopodite. Appendage III. Manprs.e like I and II, but with 8 bristles at the end of the exopodite. Appendage IV. MAxXILLULE. Coxopodite with the gnathobase bearing 8 bristles. Basipodite like I and II, but with 3 bristles on the proximal lobe. Endopodite like I and II, but with 4 bristles on the first lobe and 10 on the end lobe. Appendage V. Maxiuia like adult. Appendage VI. MaAxiLuipep (Plate 5, Fig. 5). Endopodite of 4 segments, Ist with 3 bristles, 2 with one, 3 with one and a small outer bristle, 4 with 4 bristles at the end. Appendage VII. Ist Swimmine Foor (Plate 5, Fig. 6). Endopodite with 2 segments, distal segment with 4 bristles inside, 2 terminal bristles, and one bristle outside. Exopodite with 2 segments, distal segment with 4 bristles inside, a terminal blade, and 4 thorns outside. Appendage VIII. 2np Swimmine Foor (Plate 5, Fig. 7). Endopodite with 2 segments, proximal segment with one bristle inside, distal segment with 5 bristles inside, 2 terminal bristles, and 2 bristles outside. Exopodite with 2 segments, one bristle on the proximal segment inside and a thorn outside, 5 bristles on the distal segment inside, a terminal blade, and 3 thorns outside. Appendage IX. 3rp Swimmine Foor (Plate 5, Fig. 8). Endopodite with 2 segments, one bristle on the proximal segment inside, distal segment with 3 bristles inside, 2 terminal bristles, and 2 bristles outside. EHxopodite with 2 segments, the proximal segment with one bristle inside and a thorn outside, the distal segment with 4 bristles inside, a terminal blade, and 2 thorns outside. Appendage X. 4TH Swimmine Foor (Plate 5, Fig. 9). Endopodite unsegmented, with 3 bristles. Exopodite unsegmented, with 3 bristles inside, a terminal blade, and 3 thorns outside. STAGES IN THE LIFE HISTORY OF CALANUS FINMARCHICUS. 15 Appendage XI. 5rxa Swiumrine Foor 2-lobed, each lobe with 2 hooks. Stace IV (Plate 4, Figs. 4 and 8). Very like III. Thorax with 5 free segments each with a well-developed swimming foot. Urosome of 3 segments. Appendage I. ANTENNULE with 23 segments. Appendage II. Antenna like I, but with 7 bristles on the inner lobe of the endopodite. Very like the adult. Appendage III. Manprste like I-III. Appendage IV. Maxiuuute like I-III, but the epipodite is larger with 9 bristles now like the adult, the Ist inner lobe of the basipodite has 3 bristles like the adult, endopodite with 5 bristles at the end. Appendage V. Maxitta like the adult. Appendage VI. Maxi.uirep (Plate 5, Fig. 10). Endopodite of 4 segments, 1st with 4 bristles, 2 with 2, 3 with 2 inside and one outside, terminal segment with 4 bristles. Appendage VII. Ist Swrmmine Foor (Plate 5, Fig. 11). The proxi- mal joint of the basipodite with an inside bristle. Endopodite with 2 segments, the proximal segment with an inside bristle, the distal segment with 3 inside bristles, 2 terminal bristles, and one outside bristle. Ezxopodite with 2 segments, the proximal segment with an inside bristle and an outside thorn, the distal segment with 4 bristles inside, a terminal blade, and 3 thorns outside. Appendage VIII. 2np Swimmine Foor (Plate 5, Fig. 12). The proximal segment of the basipodite with an inside bristle, the distal segment with an outside thorn. Endopodite with 2 segments, the proximal segment with one bristle inside, the distal segment with 5 bristles inside, 2 terminal bristles, and 2 bristles outside. Exopodite with 2 segments, the proximal segment with one bristle inside and a thorn outside, the distal segment with 5 bristles inside, a terminal blade, and 3 thorns outside. Appendage IX. 3rp Swimuine Foot (Plate 5, Fig. 13). The proximal segment of the basipodite with a bristle inside, the distal segment with a thorn outside. Endopodite with 2 segments, the proximal segment with one bristle inside, the distal segment with 4 bristles inside, 2 terminal bristles, and 2 bristles outside. 16 MARIE V. LEBOUR. Exopodite with 2 segments, the proximal segment with a bristle inside and a thorn outside, the distal segment with 4 bristles inside, a terminal blade, and 3 thorns outside. Appendage X. 47TH Swimmine Foor (Plate 5, Fig. 14). The proximal segment of the basipodite with an inside bristle, the distal segment with a thorn outside. Endopodite with 2 segments, the proximal segment with one bristle inside, the distal segment with 3 bristles inside, 2 terminal bristles, and 2 bristles outside. Exopodite with 2 segments, the proximal segment with an outside thorn, the distal segment with 4 bristles inside, a terminal blade, and 3 thorns outside. Appendage XI. 5rxH Swimmine Foor (Plate 5, Fig. 15). Endopodite unsegmented, with 6 bristles. Ezxzopodite unsegmented, with 3 bristles inside, a terminal blade, and 3 thorns outside. Stace V (Plate 4, Figs. 5 and 9). Body much longer, the full number of segments in the thorax and urosome. Antennules, antenne, mandibles, maxillules, maxille, and swimming feet I to IV like the adult. The maxilliped has not yet the full number of bristles (Plate 5, Fig. 16). Ist segment with 5 bristles, 2 with 3, 4 with 2 inside and one outside, terminal segment with 4 bristles. The swimming feet (Plate 5, Figs. 17-21) are all like the adult with the exception of the last, which, although having the full number of bristles, has only 2 segments to the endopodite and exopodite. Stage VI is the fully developed copepod. LITERATURE. 1902. Gran, H. H.—Das Plankton des Norwegischen Nordmeeres. Report on Norwegian Fishery and Marine Investigations. Vol. II, 1902, No. 5. 1881. GropBEn, C.—Die Entwicklungsgeschichte von Cetochilus septen- trionalis Goodsir. Arbeiten aus dem Zoologischen Institute der Universitat Wien, ete. Vol. III, Part 3. 1906. Osrre, M.—Die Metamorphose der Plankton-Copepoden der Kieler Bucht. Wissenschaftliche Meeresuntersuchungen herausgegeben von der Kommission zur Wissenschaftlichen Untersuchung der deutschen meer in Kiel, etc. N.S. Vol. 1X. Abt. Kiel. 1903. Sars, G. O.—An Account of the Crustacea of Norway. Vol. IV, Copepoda Calanoida. The work on the Copepoda of the Danish Ingolf Expedition, Vol. ITI, Part 4, 1915, by Carl With, came to hand after the present paper was in print. STAGES IN THE LIFE HISTORY OF CALANUS FINMARCHICUS. 17 EXPLANATION OF FIGURES. Pirate 1.—l. Nauplius Stage I. x 80. 2. Sad! [tle » 3. , aut 3p 4. x Bar WING % 5. ty 5 erp Vis 53 6. Copepodid ,, I. 3 PLATE 2.—1. Ist Appendage (Antennule) of Nauplius I. ee 55 . 55 3 Ti 3. oa LDL: Ass ; 3 ay LV Biv, a y V. 6. 2nd (Antenna) ; ii. Ue 5 55 ieee! Ble 8. <9 5 DE. 9: 5 % nV LO™ 5; of x ED Wee esord 45 (Mandible) a Ie eee, oe 5 JE xis PuLatTE 3.—l. 3rd Appendage (Mandible) of Nauplius ITT. 2 55 5p - 33 IV. Boe 55 53 - 3 Ve 4. 4th - (Maxillule) fn IV. Des 55 cs es V. 6. 2nd (Antenna) of Copepodid Stage TI. ford (Mandible) ‘ 8. 4th (Maxillule) 9. 5th (Maxilla) 10. 6th (Maxilliped) x 175. CX Coxopodite. B Basipodite. EP Epipodite. END Endopodite. EX Exopodite. G Gnathobase. Puatr 4.—1-5, Dorsal view of Copepodid Stages I-V. x 18. 6-9. Lateral view of Copepodid Stages II-V. x 18. Prate 5.—Distal portion of Maxilliped and Swimming Feet of Copepodid Stages IL. x 26°6. NEW SERIES.—VOL. XI. NO. 1. MARCH, 1916, B [ 18 Experiments on the Mendelian Inheritance of Eye- colour in the Amphipod Gammarus cheureuxi. By E. W. Sexton, F.LS., Marine Biological Laboratory, Plymouth, AND M. B. Wing. With Plate I. CONTENTS. yeneral conditions—habits, water, air, food, light Explanation of terms employed in paper : f 4 : ; : The pigmentation of the eye—black, red, “ all-white,” “* part-white,” and ** no-white ” The first appearance of the Red eyes Results of examinations of dredgings : Experimental work—question of sex-limitation . I. Recessives to the sixth generation JI. Dominants—Pure Blacks : Proportions of P. and H. Hybrids—Parent generation F, generation *, generation K, M, and N families Proportions of Black and Red Proportions of Pure and Hybrid Table of results Preponderance of colour Results of Black crosses Sex of survivors Records of Abnormal Eyes. : : : General notes—breeding different generations, etc. Summary PAGE 19 21 26 30 31 THE Amphipod which was used in the following experiments was described in 1913 (Journ. M.B.A., Vol. IX, pp. 542-545) under the name of Gammarus chevreuxi, and its life history was then worked out (see Sexton and Matthews, l.c., pp. 546-556). The usual colour of the eye in this species, as in the other species of genus Gammarus, is black, but several females and young with red e the yes were observed while the above work was in progress. Beyond recording INHERITANCE OF EYE-COLOUR IN GAMMARUS. 19 the fact, however (l.c., pp. 543 and 552), no special attention was given to the matter. The descendants of two original pairs taken in June, 1912, were kept under observation for moults, etc., in the Laboratory until August, 1913, when the present writers undertook to investigate the variation in eye-colour, with a view to determining first if it were a sex-limited character, and secondly, if it conformed to the Mendelian law of inheritance. In the course of these investigations we have received constant assist- ance and advice from the Director, Dr. E. J. Allen, F.R.s., at whose sug- gestion they were first undertaken, and we wish here to acknowledge our great indebtedness to him. GENERAL CONDITIONS. Before entering into the detailed results of the experiments it will be necessary to give a brief description of the habits of the species as well as of the conditions under which the animals were kept in the Laboratory. Gammarus chevreuxi is an ideal species for experimental work. It 1s very hardy, quickly reaches maturity, and breeds all the year round. The young are extruded from the marsupial pouch and another batch of eggs laid generally within 24 hours of the time of hatching. During the summer season a brood takes from 12 to 14 days to hatch, and the period of sexual activity is reached at the age of 36 days; in winter in natural conditions a brood takes 30 days to hatch, and does not become sexually mature for at least 3 months, low temperature, as would be expected, retarding development. In the Laboratory, however, which is heated in the winter, there is practically no difference in the seasons, and it therefore becomes possible to obtain several generations in the year. It may be well to state here that in this species of Gammarus the female never lays eggs unless a male is present, and also that it is absolutely im- possible for a male to fertilise two broods of eggs with one deposition of sperm. The male generally takes the female a few days before the eggs hatch, and carries it until the young are extruded from the pouch. The female then moults, assisted by the male, as described in the paper re- ferred to above (J.c., p. 550). The aperture of the oviduct is opened by the removal of the old cuticle, and the male deposits the sperm in the pouch around it, but unless the eggs are laid within a few hours they cannot be laid at all. The cuticle hardens rapidly, and a plug of the glutinous lubricatory matter which accompanies moulting and oviposition closes the aperture and hardens to the consistency of the cuticle, effectually 20 E. W. SEXTON AND M. B. WING. blocking the oviduct, until another moult takes place and the plug is sloughed with the old cuticle. Another point must be mentioned in regard to the suitability of this species for laboratory work, and that is the ease with which it adapts itself to artificial conditions. This is probably due to the fact that it comes from brackish water ditches where it is habituated to great varia- tions of temperature, salinity, pressure due to depth of water, etc. The density, for example, varies to an extraordinary degree according to the season, tides, excessive rainfall or drought, ranging from 1 to 1-028. In the experimental work, it has been necessary to keep the water as nearly as possible at the same salinity, as any sudden change of con- ditions always affects the animals’ growth and breeding. A mixture of one part of sea-water to six parts of fresh water gives the same density (1-004) as that found in the ditches when the animals were taken, and such water we have generally used. The best results have been obtained by keeping the animals in finger- bowls, generally one pair in a bowl. Each bowl contained about 200 c.cs. of water, and was covered with a glass plate to check evaporation and exclude dust. No aerating apparatus was used, the animals obtaining sufficient air for their needs from the surface of the water exposed in the bowls. In the same amount of water but with a smaller surface exposed to the air they did not flourish at all, as was found later when using jam jars and honey jars for the broods ; only a very small proportion of the young reached maturity. For food dry leaves of all kinds were used, after they had been allowed to rot in water. It was found that the animals preferred the soft tissues of the leaves of elm, hazel, and sycamore, rather than the harder leaves of oak, beech, ete. A fine delicate Ulva from the ditches they ate freely, but when the supply failed and the harder marie variety (Ulva latissima) was given, they did not eat it until it macerated. They flourish better and are much healthier with some of the mud from the ditches in the bowls, but in all these experiments we were obliged to keep the water clear, in order to watch the animals without disturbing them unnecessarily. The young are so minute—about 1 mm. in length when hatched—that they completely escape observation in the mud, clinging as they do to any particles of dirt or weed. The bowls were kept in ordinary diffused light, strong sunlight being avoided. INHERITANCE OF EYE-COLOUR IN GAMMARUS. 21 A word of explanation is necessary as to the terms employed in this paper. The Black eye-colour is dominant to the Red, and therefore Red is referred to as Recessive (R.). Black divides into Pure (P.) and Impure, but instead of the term “impure ” the word Hybrid (H.) is used. THE PIGMENTATION OF THE EYE. The structure of the eye of Gammarus has been well described and figured by Parker (“The Compound Eyes in Crustaceans,” Bull. Mus. Comp. Zool., Harvard, Vol. XXI, Plate I), the species investigated by him being the Gammarus ornatus of Milne-Edwards (=Gammarus locusta, Linn., Stebbing, Das Tierreich, V. 21, p. 476). Sections of the eye of Gammarus chevreuxt show precisely the same internal structure. The eye in this species is reniform in the adult, oval in the young animal, much raised and rounded. The superficial aspect presents a reticulation of opaque white pigment, with the ommatidia appearing as coloured spots, black or red, in the spaces of the network. The black pigment of the retinular cells of the ommatidia of the Black eye appears to be produced by a combination of black and red, even in the so-called “Pure Black” animals (Fig. 1), with a larger admixture of the red in the “ Hybrid Blacks ” (Figs. 2 and 4). The pigment of the Red eye is pure red, with no alloy of the black (Figs. 3 and 5). Sometimes the retinular cells are unpigmented and the white reticula- tion shows up in a very striking way, giving the effect of chalk-white eyes—the “ All-white” eye referred to in the paper (Figs. 8, 9, and 10). Occasionally again, some of the ommatidia are pigmented and some not ; this variation is called the “ Part-white” eye (Fig. 7). The white opaque pigment is subject to great variation, sometimes showing as faint thread-like lines, sometimes broken up and irregular, sometimes present in excess, obscuring the ommatidia, and sometimes it is entirely lacking, the ‘‘ No-white”’ eye (Fig. 6). Animals are often found with one or both eyes affected. The defect can be transmitted by normal-eyed animals to both black and red eyed offspring. Ae: E. W. SEXTON AND M. B. WING. THE FIRST APPEARANCE OF THE RED EYES. Two pairs of Gammarus chevreuxi were taken in June, 1912, those re- ferred to in the previous paper as Pair I and Pair IJ. All four animals were black-eyed. All the broods from Pair IT were black-eyed. This stock (which is re- ferred to as the “‘ Pure Black ” stock) has been kept under observation from June, 1912, till now, December, 1915, fresh black-eyed material from the ditches being added from time to time. Not a single red- eyed animal has appeared in it. The strain was tested by mating also, to make absolutely certain of its purity before using it in the experiments. The first brood from Pair I were all black-eyed: 9 young ones coming to maturity, 3 males and 6 females. The first pair to mate (Pair A) were evidently the strongest, and had the largest broods, although owing to unfavourable conditions only a few in each brood survived. The first brood from this Pair A numbered 18 ; the young were counted on hatch- ing, but not examined for eye-colour ; of these 1 male and 6 females came to maturity, one of the females with red eyes. The second brood was 28 in number, | male and 5 females surviving, and again one female had red eyes. For the third mating of the female A a different male was used (male 8), one which was freshly captured. The ensuing brood was ex- truded on October 26, 1912, 44 in number, and as these were being separated into finger-bowls for observation of moults 4 red-eyed ones were found. Male A was then put back with the female A, for the fourth mating; the brood numbered 39, 3 with red eyes. It will be seen that this female, mated with two different black-eyed males, produced some red-eyed young in each brood. No red eyes were observed in any of the other offsprmg of Pair I nor in their progeny. The four red-eyed young of the third brood died before reaching maturity, and the remainder of the brood were kept separate, each in a finger-bowl, until they were 66 days old. On December 31 they were put together in a bell-jar, and some mated at once. The first female to mate of this brood was separated from the others, and from her and her off- spring all the red-eyed stock has descended. By August 7, 1913, this female and its mate were dead, and only 20 young were found in the jar, 16 black-eyed and 4 red-eyed. The four were removed, and the black-eyed left together for three months longer ; when again examined on November 5 the numbers were 65 black-eyed and 8 red, and with these work was commenced. INHERITANCE OF EYE-COLOUR IN GAMMARUS. 23 hd The following scheme shows the origin of this red-eyed stock, clear circles indicating the red-eyed, black circles the black-eyed animals :— Ba aA PAIR /. iS @ % OY Freshly eS r 5@® 1+ brood ' ee) Ba age 9g ew see 74.8 227 brood. i Os 4° brood 40 38@ (died) hls cre ee 36.@ teosicn (died) f 4QO 16.@ Recessive Stock Hybrid Stock p. 22 P- 6 8.0 49.@ * The male of Pair A mated with two of the other females of the same brood ; the resulting young numbered 27, all black-eyed. It cannot, of course, be stated as an absolute fact that red-eyed speci- mens never occur in the ditches in natural conditions, but so far not a single one has been found, although thousands of specimens brought in at different seasons of the year have been examined. The red strain has only shown itself in the one female, female A and her progeny. It seemed possible at first that the red-eyed strain could be accounted for on Men- delian lines. If the original Pair I had been a Pure Black mated with a Hybrid Black all the offspring would have been black-eyed, half the number Pure Blacks and half Hybrid Blacks ; and if in their matings a Hybrid should mate with a Hybrid the red-eye strain should have appeared. But, as far as can be seen, only the female A had the red strain; both her mates, male A and male S, when mated with other females (some from the same brood as female A and some from other stocks) had only black-eyed offspring, and, moreover, in none of the other members of the brood nor in their offspring has the red strain appeared. It might have been that male A was a Hybrid Black and that female A was the only Hybrid Black female in the brood, but it seems pushing coincidence too far to suggest that male S captured some months later and taken at random from a large dredging should be a Hybrid and 24 E. W. SEXTON AND M. B. WING. the only Hybrid in it. None of the others captured then or at any other time have shown the red strain. One series of 5000 was counted, for example, and all were black-eyed. Considering, however, that this way of examining the eyes was not a sufficiently accurate test, it was decided to take two dredgings, a winter one and a summer one, of as many animals as could be found at the time in all the ditches as the result of a day’s collecting. These were to be counted, each one examined for eye-colour, each ovigerous female to be separated until its brood hatched, and each brood to be counted and examined. A number of adults were to be taken and mated with red- eyed mates, and their young examined. And finally, the most im- portant test of all, a number of mated pairs were to be kept and bred to the F, generation, to see if captivity and inbreeding would repeat the result obtained with the Pair I of June, 1912. The first dredging for this purpose was made on February 11, 1915, 373 animals, all black-eyed, were found, 198 of which were adult females ; the greater part of the remaining 175 specimens were males, the rest were immature. Of the females, 112 had eggs, the others, 86 in number, were paired. The 112 ovigerous females were separated, and their young counted on extrusion. The broods in many cases were small, many of the animals having apparently not long reached maturity ; e.g. the first broods to hatch were in number as follows: 11, 3, 15, 4, 9,11. In all, the number of young extruded was 641, all of them black-eyed. Forty-six adults were mated with Red mates ; all produced black-eyed offspring, proving beyond doubt that they were Pure Black and not Hybrid. The number of broods counted was 62, the number of young 853. Twelve of the 86 black-eyed pairs brought in from the ditches were taken to breed to the second generation of offspring. Of these Pairs II to XII * were kept for two or three broods each, and then returned to the rest of the dredging. The total number of young in the first generation of ofispring from these broods was 473, all black-eyed. For the second generation, one brood from each of the Pairs II to XII was taken, the first to mature in each case. This was done because the red eyes appeared in the first brood of the first F, pair of the original stock (p. 22). When these broods reached maturity some of the mated pairs were separated and the others allowed to mate in the brood-bowl, the young in all cases being removed as soon as possible and examined for eye-colour. * Pair I produced no young, the female throwing off the eggs; the male was then paired with three other females, two Black from the dredging, and one Red from the old stock ; all laid eggs, but no young were hatched, and the male died. INHERITANCE OF EYE-COLOUR IN GAMMARUS. 25 215 young were counted, all black-eyed ; some of these have commenced breeding. This generation is very interesting from the fact that in it, as in the same generation of the original stock, a deviation from the normal occurred. In the case of the original stock the black pigment was absent, and the result was a red eye with the superficial network of opaque white pigment unaltered. In this second case the black pigment was present in every instance, but in the broods of Pair V the white pigment was affected in greater or less degree. The female of this pair had less white than is usual in the eye—the reticulation was perfect, but the lines of white were very thin and thread-like. The eyes of the young in the first generation were the same, but in the young from the first pair of these that mated there was considerable variation. One brood of 13 contained 2 young with “‘ no-white” eyes on both sides (Fig. 6), 5 others with the white reticulation very faintly marked, and 6 with eyes like the male parent and female grandparent. This brood is being kept separate to see if the defect follows the Mendelian lines of inheritance of characters. No individuals of the third generation from these pairs have been hatched yet (Nov. 19, 1915), but 60 which have been examined from the General Stock bowl all have normal black eyes. The summer dredging was taken on July 6, 1915. 372 hving animals were examined, all black-eyed. A good many more were brought in, but did not survive overnight, owing to the heat and overcrowding of the pots and consequent fouling of the water. Twenty-two adults were mated with Red mates; 31 broods were counted, containing 348 young, all black-eyed. Thirteen black-eyed pairs of those paired in the ditches were separated from the others, and placed in finger-bowls to breed to the second genera- tion. By November 19, 1915, there were 127 of the first generation and one brood, 5 in number, of the second generation, all with black eyes and all normal except the offspring of one pair. In this bowl, four of the first generation were left, two females with normal eyes, and two from a younger brood, one with normal eyes, and the other with a white patch on each eye at the upper end caused by three or four of the ommatidia being unpigmented, the “ part-white ” eye (cf. Fig. 7 for an example of this in the Recessives). This is the first occurrence recorded in the course of the work of a variation appearing in the first generation from animals brought in from the ditches.* * Only one specimen has been recorded from freshly captured animals, a male, with the left eye affected. 26 E. W. SEXTON AND M. B. WING. EXPERIMENTAL WORK, The first question to be decided was whether the red eye-colour was a sex-limited character or not—the only adult specimens previously observed having been females. In order to settle this point the 8 red-eyed young found on November 5 (p. 22) were placed in a bowl by themselves to come to maturity. It is impossible to distinguish males from females until the animals reach sexual maturity, which occurs when they are about half-grown, the males being then easily distinguishable by the fine coiled hairs of the lower antennze, and by the larger gnathopods. The 4 red-eyed young of August 7 were kept in the Laboratory, only two coming to maturity, both female. The 8 red-eyed young of November 5 were kept in another room, not heated, with a temperature ranging from 4°—10° C., and were in conse- quence much slower in maturing ; but in three months’ time both males and females were seen—thus settling the question of the red eye-colour being a sex-limited character. In February three pairs mated. These were kept separate, each pair in a finger-bowl to itself, and the others, which were females, with the two August 7 females, were paired with males from the ‘“‘ Pure Black ” stock. Males and females paired were also taken from this stock, and thus we had Recessive mated with Recessive (R.x R.), Pure Black mated with Recessive (P.xR.), and Pure Black mated with Pure Black (P.xP.). We started daily observations and records on this generation, calling it the Parent Generation, and counting from it the F,, F,, etc. Our aim now was to discover if the Mendelian laws of inheritance of characters were applicable to the results of these crosses, and the ex- periments to this end will be given in detail under the different divisions —I Recessives and IIT Dominants. I. THE RECESSIVES. We commenced work in February, 1914, with the three pairs just referred to, adding in May seven pairs taken from the 42 red-eyed animals hatched since November 5, 1913, in the Hybrid Stock (see p. 22). Hach pair and its offspring have been kept separate, the broods on hatching removed from the parents’ finger-bowl and examined for eye-colour, each brood being numbered and set aside to come to maturity. In every case in which both parents were red-eyed all the offspring have been red-eyed. The red-eyed animals appear to be more delicate than the black-eyed, shorter-lived, and less fertile. They are quite as large and as active, and INHERITANCE OF EYE-COLOUR IN GAMMARUS. at in many cases observed, reached maturity before the black-eyed in the same brood. Yet, if left to breed together with no admixture of the black- eyed strain, they gradually diminish in numbers, throwing off the eggs sometimes soon after deposition, or dying after having had only one or two broods. Seven of the ten stocks have failed in this way. The results of the Experiments with the Parent Generation are given below in detail, and are typical of'all the experiments with inbreeding Recessives. They are as follows :— Exp. 1. Two broods, 10 and 12 respectively ; female died. , 2. Mated, but no eggs laid. ,, 93. One brood ; only | young hatched. ,, 4. One brood of 20 young. ,, 9. First brood, only 1 young hatched ; second brood, 3 young. Thinking the small numbers might be due to some defect or unhealthiness in this male, it was taken away and another added. Third brood, only 1 young hatched, Male again changed. Fourth brood, 14 young; fifth brood, eggs thrown off before hatching. Male again changed. Sixth brood, 17 young. ,, 6. One brood, 19 young. A second brood was laid, but the female died before the eggs were hatched. ,. 1. Mated, eggs laid, but thrown off before hatching, probably un- fertilised. ,, 8. Mated, eggs thrown off as in Exp. 7. ,, 9. One brood, 10 young. A second brood was laid, but the eggs were thrown off before hatching. , 10. Mated, eggs thrown off as in Exps. 7 and 8. ,, 11. Mated, eggs thrown off as in Exps. 7 and 8. The total results for six months for the Parent Generation were: One pair mated, no eggs laid; seven broods not hatched; eleven broods hatched, the young numbering in all 108; average per brood 9:8. Only about half of these survived to maturity. In the next generation, the F,, a rather different system was followed. In some cases records of separate pairs were kept, in other cases the whole brood was left together in a finger-bowl, each female removed after oviposition, kept separate until the eggs were hatched, and then returned to the brood-bowl to mate again. The total results in the twelve months from July, 1914, to July, 1915, for the breeding of the F, generation are: 2 pairs mated with no results ; 80 broods from the other pairs, 20 of these not hatched, 60 hatched, 28 E. W. SEXTON AND M. B. WING. numbering 422 young (these are the F, generation), average 7 per brood, a smaller average than in the preceding generation. In the F’, generation the same system was followed as in the F,, the ovigerous females being removed from the brood-bow] till they had ex- truded their young, and then returned to it. But in one or two cases where only males or only females were left of a brood, mates from a different brood, but of the same family and the same generation, were added. These records were kept separately. The females of the first category laid 26 broods between September, 1914, and October, 1915, and hatched 207 young. One pair mated twice with no results, and two other pairs also mated with no results. In the second case, where male and female came from different broods, only two broods, of 7 and 8 young respectively, were hatched, the male in each case dying soon after, but these broods appear stronger than the others. Several of this F, generation are still breeding (Nov. 3, 1915), but the numbers already obtained are sufficient for proof and record. Of the F, generation 105 have survived (Nov. 19, 1915), many of them not yet mature. In several broods all the individuals have very pale eyes, with hardly any of the red pigment showing. The results for this genera- tion are unsatisfactory, only a few young being hatched. Ten pairs have mated so far, as follows :— From the first category (individuals of the same brood paired in their brood-bowl) 2 pairs mated, no eggs laid; 1 pair mated, eggs thrown off ; 3 pairs with 18 young in 4 broods. From the second category, which appears to yield a stronger stock (the two F, broods of the two F, pairs in which male and female came from different parents), 4 survive of the first brood of 7, not yet mature; the second brood of 8 matured, and 6 matings have taken place: 4 young (all dead now); eggs thrown off; no eggs; 9 young (all dead); 7 young (1 left) ; and 5 young (3 left, mature females). The total number for the F,4 generation thus far is only 31. Some individuals of one brood, the 9 young referred to above, came to maturity, and 2 broods of #’, were hatched, numbering 12 young. Of these 9 sur- vived, and are now nearly ready to breed. II. THE: DOMINANTS. The Dominants are divided into Pure Black and Hybrid Black, which will be dealt with under separate divisions. Aecording to the Mendelian laws of inheritance of characters, the INHERITANCE OF EYE-COLOUR IN GAMMARUS. 29 matings of the Dominants with other Dominants and with Recessives should show the following results :— (a) P.xP.: mating of Pure Black with Pure Black should give all black-eyed offspring, Pure Black, which should breed true through all succeeding generations. (b) P.xH.: matings of Pure Black with Hybrid Black should give all black-eyed offspring, half Pure Black and half Hybrid Black. (c) P.xR.: mating of Pure Black with Recessives should give all black-eyed offspring, Hybrid Black, which when bred together should show the red-eyed strain in the next generation. (d) H.x H.: matings of Hybrid Black with Hybrid Black should give three black-eyed offspring to one red-eyed, 1.e. in the proportion of one Pure Black and two Hybrid Black to one Recessive. (e) H.xR.: matings of Hybrid Black with Recessive should give off- spring half of which would be Hybrid Black and half Recessive. THE PurRE BLACKS. Only a short note is necessary under this heading. The Pure Black stock (p. 22) has been kept and interbred for over three years inalargejar. Observations have been made on it at different seasons of the year, all the animals being taken out and examined for eye-colour. Different pairs also have been kept separate from time to time and their progeny recorded to the third and fourth generations, but in all the cases not a single red-eyed one has been found. With other dredgings brought in at intervals since June, 1912, the same results have been obtained. The last dredgings examined were those described on p. 25. With regard to the 194 young from the P. x P. matings mentioned on p- 41, the record of the number of their offspring has not been kept, it having been thought sufficient to examine the eye-colour of all the animals in the different bowls from time to time to make sure that no red-eved one appears. In the P. x H. matings which have been tried, the young were all black- eyed. The difficulty with these has been in bringing a sufficient number of any one brood to maturity in order to test them for P. and H. characters. Only one case succeeded well enough to be recorded, the Brood 1 of Experiment 118 referred to on p. 41. Twenty-two young were hatched, and twenty-one reached maturity—seven males, thirteen females, and one abnormal one. Each of these was mated with a red-eyed mate except 30 E. W. SEXTON AND M. B. WING. in the two instances noted, when a proved Hybrid mate was used, with the following results :— P.? 13 young. Black. Hey A205", 67 Black and 53 Red. 2 2 4 mates, 2 P. and2R. 5 broods laid, none hatched. P.3 64 young. Black. Te a 8 Black and 6 Red. EZOP nO: # Black. BAe Side Black. Peto: Black. The eye of this female is figured. See Fig. 1. 1 ef CO 5 Chae sae Black. His@s. mien 5 Black and 3 Red. Minky Black. Female eaten. aaa 11 Black and 4 Red. Heo fA ine. 3 Black and 1 Red. This female was tested with a Hybrid Black mate. Ens, 10 Black and 4 Red. Also with a Hybrid Black mate. 4S Katen by mate. 1s ei 5 la 31 Black and 26 Red. Por 20°", 12 Black and 8 Red. Peo. Black. Hee 2a 12 Black and 12 Red. Reo. wo Black. 2 2 This is the Abnormal one mentioned above. In the third cross (c) P. x R., the matings have always produced black- eyed offspring, all Hybrid Black. The figures obtained in the F, genera- tion may be quoted here—1563 young (see p. 39), as well as those of the Parent generation given in the next paragraph. THe Hysrips. Parent generation. In the Parent generation 33 experiments were made, starting in November, 1913, Pure Black males being mated with Recessive females, and Recessive males with Pure Black females, 16 experiments with the first cross, and 17 with the second. There were 18 broods hatched from the first cross P. 3g x R.9, numbering in all 323 young; and 21 broods from the second cross R. 3 x P. 2 with 313 young. In all these experiments without exception, the young had black eyes. In the first cross some paired without results, the others had from one to six broods each, the largest number in a single brood being 38. In the INHERITANCE OF EYE-COLOUR IN GAMMARUS. ou second cross, all but one of the broods were hatched, the largest number being 49. F, generation. All the young of this generation were black-eyed, as was to be expected, in accordance with the Mendelian law that the offspring of Dominant mated with Recessive resemble the dominant parent in character. The further development of the law, that though the offspring are dominant in appearance, yet in constitution they are hybrid, could not be deter- mined until the next generation, the F,, appeared, the eye-colour alone not being a sufficiently accurate guide in distinguishing Pure Blacks from Hybrid Blacks. In order to make sure of each individual F, and to keep its history clear, all the F, broods were kept in separate bowls till mature, and then as each pair mated it was removed and records kept of all the matings, the young being counted and examined for eye-colour immediately after extrusion from the pouch. All the F, that reached maturity were tested and all proved Hybrid Blacks. The results for the eye-colour in the F, generation are given below. F, generation. The first idea was to take the F,, broods in order as they hatched to the number of 1000 young, and to find if the proportions held good—three black to one red. Seventy-four broods were taken in this way, the young numbering 586, 437 of which were black-eyed and 149 red-eyed, the reds therefore being very slightly in excess of the theoretical figure. These broods appeared during the summer months, when the animals mature more rapidly and have a much quicker succession of broods than in the lower temperature. As the numbers in the broods were decreasing, the adults dying off, and the whole of the stock looking unhealthy, it was thought well to strengthen it before continuing the experiment. A change of food was given, and plenty of mud from the ditches. It was then decided to pick out the three largest and strongest of the F, broods, and to count all the F, progeny produced by them. K, M, and N broods, which had matured under the healthier conditions, were chosen—K_ brood consisted of five males and nineteen females, M of nine males and six females, and N of fifteen males and seven females. The first 72 broods from these three families (from Oct. 22, 1914, to March 2, 1915) contained 1004 young, 753 black-eyed and 251 red- eyed, in the exact proportion, as will be seen, of 3 to 1. K family was represented by 43 broods, total number of young hatched 655, of which 487 were Black and 168 Red; M family by 19 broods, 271 young, 204 32 E. W. SEXTON AND M. B. WING. Black and 67 Red; and N family by 10 broods, 78 young, 62 Black and 16 Red. By this time the animals were beginning to die out. N family was finished by June 16, 1915; M family on that date had only 1 male and 4 females left (this male died on July 22); while K family still had 3 males and 16 females. The next 65 broods (to May 24, 1915) brought the number of young extruded to 2000=1505 Black and 495 Red: K family with 1228, 924 Black and 304 Red; M family with 582, 438 Black and 144 Red; and N family with 190, 143 Black and 47 Red. The number 3001 was reached on July 24, 1915, total number of Black 2270, and of Red 731; K family with 1540 Black and 490 Red; M family with 552 Black and 181 Red; and N family with 178 Black and 60 Red. The figures therefore for the second and third thousand give to the Blacks a slight excess over the theoretical figure. In the first thousand (1004) the proportions, three Black to one Red, were exact; in the 2000 they were very nearly right; but in the 3000 the Black rather predomi- nated, the fact that the Black is the hardier strain probably accounting for this. This same slight but steady increase can be seen on a small scale in the detailed Brood-records of the Hybrid crosses H.R. In the first broods of each pair the proportions are nearly always exact, half Black and half Red, but the total results for all the broods show a preponderance of Black (see lists, p. 35); compare also for an example of a single brood Exp. 85, p. 38. In Exp. 85 Brood 1 numbered 24 = 12 Black, 12 Red. Bag 12 Oia Sie) Wake SOM und. DS relate, Mgt a 4 985-914 nae alae Leb 9078s teOoy teri asi Gauge: 29, 90% say oO Pan * ie See ee Olas 8 sth Ontaaee Sides 9 : [4 Sve 6.18 EEO oe) 26 1 yeu. t aula 11 ¥ 34 15y Bee 1977 x 12 2 Np Set ISN Po ie. 13 mF 26 al ae Aas Total .- 13 broods. *°332 176 Black. 156 Red: voung, INHERITANCE OF EYE-COLOUR IN GAMMARUS. on The records of the individual families are very interesting. In K family, in which females preponderate, breeding commenced October 25, 1914, the first thousand was reached on April 20, 1915: 63 broods hatched out numbering in all 1007 young, of which 756 were Black and 251 were Red, exact proportions. In the second thousand there were 59 broods hatched containing 1003 young, 767 Black as against 236 Red, the Black therefore in excess. 23 more broods were laid with 431 young, 336 Black and 95 Red. As will be seen, the proportion of Black is again higher. The last male died on September 21, 1915, on which date the records were perforce brought to a conclusion. These figures prove conclusively that in the F, generation the pro- portions are 3 black-eyed to 1 red-eyed. The next step was the testing the black-eyed F, to get the proportion of Pure Black to Hybrid Black, but the results of this work are not exact and naturally cannot be. It is easy enough to separate the colours, black from red, immediately on hatching, but impossible to determine the question of the constitution of the black-eyed until they breed. Owing to various causes a high rate of mortality has to be allowed for, and the results therefore can only be given on the survivors. The animals undergo many ecdyses, the young every few days, the adults at longer intervals, the males again at much longer intervals than the females. The moulting period is always critical even to the strong ones. It is absolutely fatal to the weakly ones in a brood, the others attacking them in their feeble condition and devouring them. With the adults the mortality is higher among the females. The reason is that the male carrying the female for some days prior to the extrusion of a brood, and assisting it through the moult which immediately precedes the de- position of a fresh brood, very frequently ends by eating it directly after. A great many females have been lost in this way in the course of the work. But the principal cause of the high death rate is the development of injurious bacteria in the bowls. At first it was thought that the bacteria had been introduced with the rotting leaves given as food, and many methods of sterilising the leaves were tried. After a while it was noticed that all the broods set out on a certain date had perished, and on com- paring this result with a similar one in Mr. Crawshay’s experiments, he discovered that the same sea-water had been used in all, and that this water was infected, although taken as far out as the Eddystone for the sake of avoiding shore contamination. Several kinds of bacteria have been observed, some fatal within a day or two, some after several weeks, and others which, except for retarding development, do not injure the animal. One of this last-mentioned kind turns the water a milky colour, and forms dense slimy masses all round NEW SERIES.—VOL. XI. NO. 1. MARCH, 1916. C 34 E. W. SEXTON AND M. B. WING. the bowl, and over the food, and even clings to the amphipods themselves. With a lens it is easy to see long streamers of this slime trailing behind the little creatures as they swim. Proportions of Pure Black to Hybrid Black in the F, generation, The experiments to find the proportions of Pure Black and Hybrid Black were made with the surviving F, progeny of the first F, brood, Brood A, that came to maturity. The following table shows the parentage with the number of young hatched, 210 in all, 153 black-eyed and 57 red- eyed. P.3 x R.2 Parent generation. (From Pure Black stock.) | (One of the 8 Reds, p. 26.) First Brood—Brood A =22 young. Hybrid. F', generation. extruded 16.3.1914. A.F, pair. B.F, pair. | C.F, pair. | D.F, pair. | E.F, pair. | F.F, pair. | G.F,. 4 broods. | 4broods. | Ibrood. | 2 broods. | 3 broods, 2 broods. 1 brood. 55 young. 48 young. 7 young. 20 young. 43 young. 27 young. 10 young. EF, generation. Hatched :— 38 Black. 37 Black. 6 Black. 15 Black. 30 Black. 21 Black. 6 Black. 17 Red. 11 Red. 1 Red. 5 Red. 13 Red. 6 Red. 4 Red. Survived :— 23 Black. 15 Black. 4 Black. 13 Black. 18 Black. 15 Black. 5 Black. 10 Red. 7 Red. 0 Red. 3 Red. 7 Red. 4 Red. 3 Red. Only 127 reached maturity, 93 black-eyed and 34 red. Of the Black 44 were males and 49 females ; of the Red 20 were males and 14 females. The testing was done with red-eyed mates, the Blacks being separated into finger-bowls and each given a Red mate. The resulting broods would at once show the P. or H. character, for if the black-eyed animal were a Pure Black the offspring would be all black-eyed ; if a Hybrid -Black, half the young would be black-eyed and half red-eyed. Later, when the constitution of each had been determined, the survivors were mated together: “P.X(P = Seige he x ie Sand! dese It sometimes happens that the individuals of the first brood of Hybrid x Recessive, if few in number, are all of one eye-colour, not the normal proportions, half red and half black. This occurred six times in the course of these experiments ; in four broods the young were all black-eyed ; in two, all red; the highest number in any of these broods was four. To avoid error each pair was kept for at least three broods to make quite sure of the constitution ; in some cases the black-eyed were mated with two or three different red-eyed mates. In all 141 experiments were made with the 93 Black-eyed animals. Thirteen, 7 males and 6 females, died without proof, probably through INHERITANCE OF EYE-COLOUR IN GAMMARUS. 35 some inherent weakness; im one or two cases broods of eggs were laid but not hatched, in others the stronger mate ate the weaker one. Of the 80 that survived, 22 proved Pure Black, 8 males and 14 females, and 58 proved Hybrid Black, 29 males and 29 females. Ten experiments were made with P. males, 24 with P. females, 38 with H. males, and 56 with H. females. The details of the experiments are as follows :— TABLE showing the details of the experiments made with the black-eyed F, progeny of one brood of the F, generation of Hybrids, from September, 1914, to September, 1915, in order to find the proportion of Pure Black to Hybrid Black. Theoretically it should be 1 P. : 2 H., but, as has been already explained, the results recorded here cannot be considered exact owing to the high mortality amongst the immature. Experi- Black. Number Byercolour: Number i oe s ment of Young of Pure Black or Hybrid Black. Number. ¢ @ hatched. Black. Red. Broods. Exp. 1 — 2 No results : 9 eaten. a ene D No results : Q died. Mero = Oy — — -= = No results : 9 died. 5 4@ 3) - ( No results. meee B90) SATE & 2) die “| ps eles Serie iGe rip) 35> lA rm Ost O25 15 10 2 ie Om: S| j No results. pe obo, 85} 14 3° Ee erie la! ogi) yt © yee } (No results. a Lore © No results : 9 died. Seite 5GIh 34 1 299 AE Paes i 2 — 2 ie ql 1S EO oy Ce a} 2. Ge ee ors OP)! 98 Aee aa Pl sole eat 10 OF ed. Lo ,,/ | Eggs laid, not hatched. Peale soo Ap Sep! » 20a 3] iene results. » 206 ,,- — 9 t 9) ie neh perene ) SaaS yao, * 99 ee Se a - No results: ¢ died. 22 — @Q - No results: 9 eaten. 36 EK. W. SEXTON AND ‘ee Black. pape Eye-colour. Maer Number. $ @ hatched. Black. Red. Broods. Exp. 23a — 2] = = = = oO a5 Pal 2 i 1 » 236 — i, 22 10 12 2 » 24a — *\ PA 12 9 3 5, 246. — ,,2. 6 1 5 1 SD) Oe 6 5 i » 26a — ¥| 266 — ,,; 70 31 oo 4 » 26¢ — ‘| a A Oe all 7 4 i » 2a 8) = POS ae NGS © ie 22 G0 4 ie OG tee tea) ae) 3 2 1 OD cee) BG han 19) et lan 3 p30 part Oogles 5 4 ] 1 tee | — 9 23 11 12 1 2S ae = = _ Sap se VO ae 95 2 Sou Ca =e == = 53a — 2, ei GPA 2 34a — Q 8 All - 2 345 — i 14 cy — 2 34¢ — =) 67 a — 5 POI oe—— Ol 13 3 10 1 30b — i 10 8 2 ] Mec. pi aoe” as? 2 ee Oa —— teil re: 20 14 2 30 . — 30. BnoS All — 4 31a — *] 3D 16 19 2 oa — ,- «6 43 33 2 31C — 4 5 4 ] 1 eC el edt All -- 4 So eee SB} 2 meo9D — O\ — » oye — ,,)| — Paso? | 35 “26 9 3 39e€ — 4 Hs = = — 40 — Q-— 25 All —- 2 44 —®@ 8] 42 39 4 Sate itu LS All ~ 3 AMpa= ) dof 4 1 M. B. WING. Pure Black or Hybrid Black. ee results. 18). [ae results. -H. Lo results. H: ( No results: ate its mate. a. ine > H. Ef { No results. eae ( No results. Up. P. \ | Mi ee if iP: INHERITANCE OF EYE-COLOUR IN GAMMARUS. 3d Sa Black. 2 ae Eye-colonr, ae Pure Black or Hybrid Black. Number. $ @ hatched. Black. Red. Broods, Exp.43 3g — — -— -No results: ¢ killed by » 44 -- @ 35 16 19 2 EL. [mate. » 45a — ml 9... VAI — Lee ed biba tv.) DO i oe Cage es » 464 gs — 10 6 4 2 Fi, » 41a oT 29 12 17 ay aah ae ATO. UNo results : 3 died. ,» 48a — ia 19 ~All -= rae 1 ee i Sen a ign | ees » 49a — 2) 30 16 14 2 Ee » 496 — ,,/ 18 13 5 1 - » 00 — Q 26 10 16 3 Et ISD. =) O84 32 2 3 H. » 2 fg — 4i1 All -- 2 Pe ea —= 2 82 All — 4 P. , DA(1)S -- No results. , BA(2) 3 - J » 94(3) 3 ; ss » 2 — 2 108 All —- 5 Pp: » 06 — Q No results. » dla — ca 30 14 16 2 fae » d1b — ,,; 63 36 27 2 See » oc — | 135 65 70 5 k Doe ae — - —- — {No results: ? eaten. ee opee =o. SATIS —— 3 TEP: Pero), (gos alll 7 63 54 4 H. 5 Gla 2,27 58 34 24 Sop. & 6g. ,,) ald. Al 4 rea | ae 3 ~H. a . No results: eggs thrown | off: 9 died. iP. B Oar -— 9 81 All —- 4 mean No results: ate 2: died oo —- 2 63 All — = 4 Pp [in moulting. ,» 66a — *} 12 All — i ie Pach = ito: 1 F< tO I » 66¢ — 4 131 a — 3 | MOG oh 2 12 9 2 38 E. W. SEXTON AND M. B. WING. Number vrhont Black. satis Eye-colour, “of Pure Black or Hybrid Black. Number. $ @ hatched. Black. Red. Broods. xpaOde—— (Oates, (ve are results : too young ? Ob ==.) 135, UAll) Ge 7 » tla — 2) 118 63 5D 4 a ,» (lb — ,, Je — — — al result : 2 eaten. » (2a — *| S) 7 2 1 wb) — Gee oo 16 ee 1, Bae 5 (20 | 27 11 16 1 | 1 Ertl ae BC aa 19 5 14 1 He » (4a — 2) 26 \1 15 3.0 ye hee es 3 4 1. ales » (oa — 9) 64 33 Bil 2 “pH Eb eG 8 1 ahs POW, se 23 24 4 iby ite 3 =O, SHG 6 14 4 iAH do Go == ow All -- 2 RP. » 9 gs — 28 14 14 2 Hi » oO” go. = 1 a ] No results of. value: olla G ==) 700 All = 4 Pe [3 eaten. S820 alae 2 6 3 AY ed, ooh.) == shOGs CHE 15 declaw Cote Go — ool, ~1ge S156 13 i. ion eh: =. LOL 95 96 10 ick , 39a f | — — No results: ate 9. Lar SObe We) eur 3 1 es 18 2 90K So 59 All 2 iP, tele eh = * BT 31 26 5 iH. se 926 Sh == 185 95 88 10 He 3, Od == Pe 82 15 17 1 fez aye ea — No results: eggs thrown | off. p94. Oifesh 253 21 32 4 1EB » 9 — Q 146 68 78 6 i. » 9 fg — 94 54 40 6 H. Heo Gi = 2 1 1 2 A. » 98 gg — 209 95 (114 12 Hi en OOmeG | SO All — if ie S100 =f -—- 10 6 4 1 H. Os Ss — 256, 140° S116 10 Et. Totall41 37 435494 3555 1939 323 P.=8¢ and 14 9. Exps. ¢ ¢ Young. Black. Red. Broods. H,—29 $ and 29 9. INHERITANCE OF EYE-COLOUR IN GAMMARUS. 39 The total number of young hatched was 5494. Of this number 388 were the black-eyed offspring of P. j x R.@ and 1175 of P.? x R. 3. The number of young from the other cross, H. x R., was 3931—1992 Black-eyed and 1939 Red-eyed—1134 Black and 1098 Red in the mating H. 3 x R. 9, and 858 Black and 841 Red in the mating H.? x R. 3. As will be seen, the proportion is not quite exact, the Blacks being rather in excess. It appears to vary a good deal with the individual, though perhaps the number of offspring from a single pair is not sufficiently large to eliminate mere chance variation. Some animals have a succession of broods fairly evenly divided into Black and Red, while others have a preponderance of one colour or the other, others, again, having first one brood unevenly divided, the next restoring the balance, and so on. Ex- amples of the first will be found in Exps. 87 and 57. In Exp. 87 (9 H., with the same mate for all the broods)— Brood 1 numbered 27 — 14 Black and 13 Red. nO ig Tee gua Se ae ieee pity Some a ae = ey bah. oe MO [Qe 55 ‘ mou CROC Tey: [eis be 4s mea. = 20 = 10 ee Nise § fae Sayan ts ont aera sist | ac Gara 30r = 914 ga Digit EOLA», 4 — 12 ae 19 191 — 95 Se o6kt, Exp. 57 (2 H., with 3 different mates)— Brood 1 numbered 8 — 3 Black and 5 Red. ae ss 22 = 11 a 1 ae eet . a0) — 16 Hs Lae MarR enta fats 33 = 20 Pais Seis reese) x Piles Wl: 4 LOR. | ates Get phe wie. Cee? Oh Pe he aaieal| 20°= 8 m foro | Je 8 ss aoe 20 Ke nS Gober. “G <- th eee 1G ie 998 —115 otis. For examples of the preponderance of one colour Exps. 60, 61, 71, and 95 will serve; 60 isa ¢ H. and 71a? H., both had 4 broodsfeach,§with 117 and 118 young respectively. 40 E. W. SEXTON AND M. B. WING. In Exp. 60— Brood 1 numbered 11 = 7 Black and 4 Red. be x 28 = 12 ns Oe. 4s REO , eee zs ROC ee. es 31 = 16 35 LO) os, Li 463 de aaa In Exp. 71— Brood 1 numbered 12 Mil bast: = ai " 7 Me ate AN 909 LA sath site: 5: 41 = 18 : (18 = "63 slboialSt In Exp. 61 the Black are in excess. Brood 1 numbered 8 ” 2 ” 21 = 12 ” 9 cB) 3 ” 29 = 18 ” dal ge eee 1 ule Ud ==F45 5 28 In Exp. 95 the Red preponderate (cf. Exp. 7 Black and 8 Red. Brood 1 numbered 15 Soo: S WAS ies . es. om ea Z a ae Sas A oe T= BS . see ae 33 als N 146 — 68 a =} For illustrations of broods u Exps. 32 and 72 may be given. 51). 9 4 Black and 4 Red. be) 99 be) >) Exp 32. Brood 1 with 23 = 10 Black and 13 Red. es eas eh, Ok 50U= ake Saas Exp. 72. Brood 1 with 9 =. 7 Black and 2 Red. ” 2 re) 33 = 16 ” 17 ” ” 3 ” PAT) sea td ” 16 9 695 =o ao 1; INHERITANCE OF EYE-COLOUR IN GAMMARUS. 41 The H. ¢ of Exp. 75 had two broods of 21—1n one case 13 Black and 8 Red, in the other 13 Red and 8 Black. The number of young in a brood varies with the individual, but the numbers in the broods of a single pair do not vary much asa rule; to take an example, Exp. 99 had seven broods as follows: 11, 15, 13, 10, 11, 15, 11. Exp. 35 is an interesting one, showing the varying proportions of Black and Red with different mates. This female was mated with four males with the following results : with male a, one brood of 13 young, 3 Black, 10 Red ; with male b, one brood of 10, 8 Black, 2 Red ; with male c, two broods of 28 and 27, with 12 Black and 16 Red, and 11 Black and 16 Red respectively ; and with male d, two broods of 11 and 23, with 6 Black and 5 Red, and 14 Black and 9 Red respectively. Many of the F, animals had died by the time these experiments were finished, only a few remained to be mated together. Two matings of P. x P. were made, the other P. animals being paired with H. mates. IEaSCE. Exp. 83a 5 broods 133 Black-eyed young. ¢ died. ‘ ie ae 61 p @died! Pec H. ,» 84 Ibrood Eggs thrown off. S died. E 3s = 5 is = Pr) > 5 2H = ) cI 5 = o SI a Gee Ae 5, | Aa hi cs cs E Fa 5 B P.xR. 10 106 83 | 50 33 R. x P. 25 299 |. 240- | 129 111 H.x R. 43 ; 551 387 955 S100 282 196 90 101 269 191 RixH. | 37 510 Sewriiison) “losa Mieeo 1 ism. WT 92 241 164 Broods in which less than 50 % survived. P.XR.. | -10 142 Silky, eeliGnn. 1S R.x P. 26 492 Gill foarte Ag Blaek | Crosses 12 Seg 7 194 79 | 40 39 PoSeee 5 57 28 10 18 Eesce 9 169 40 17 23 HesxeH! 13 286 30 i 15 220 eg, 6 Z 66 8 RECORDS OF ABNORMAL EYES: ‘“NO-WHITE,” * PART-WHITE,” AND “ ALL-WHITE.” Attempts at breeding the animals together to ascertain if the “ no- white,” “‘ part-white,” and “ all-white ” variations follow the Mendelian lines of inheritance have so far not succeeded, although these abnormalities seem to run in certain families and not in others. For example, in the F, Hybrids (p. 31) a great number of cases occurred in Families A and K, only one case in M, and none in the other families. _ Some instances may be given in illustration of the proportions and degree per brood of the “ no-white”’ variation. In K family at least six normal-eyed females transmitted this strain, some more than others, and the proportion of “* no-white ”’-eyed in their broods was much higher than in A family. These females mated in the brood-bowl and were removed to extrude their young, and then returned to the bowl to mate again. During the month of June, 1915, 20 broods were extruded by the different K females (some of them having two broods each in the month), and 44 E. W. SEXTON AND M. B. WING. in 10 of the broods “ no-white”’-eyed individuals were found, as follows :-- 14 young: 2, Je uaes Lo; 28 30 (2 broods 23 _,, together) 17 young : las eeaers 11 Black, 3 Red; amongst them 2 Black “ no-white.” B28 ghee Bane i Aine! (oe ey , opt oe 2 Red % Dee LON Sy ee 1 Black i a ee eee; " One, % Dice emotes # bynes ss 1 Red i Tibi tao EG 5 Black 2 Red 14 ak Se = 4 Black ra i en | ‘ 5 In the A family 7 animals out of the 93 black-eyed (p. 34) produced ¢ some “‘ no-white ’-eyed young, 1 male and 2 females from Af,, 1 male and | female from Df,, | male from Ef,, and 1 male from Ff,. The details are as follows :—- In Exp. 28. Brood III. 1 Black “ no-white”’ on one side, and 1 Red fot Be in wriGO), busi: e403. ‘“no-white ” both sides. The Black was a female, the Red died before maturity. The 3 of this experiment mated with the 2 in Exp. 27 and had 1 Black abnormal 2 in Brood III. “ I. 2 ‘ no-white ’? Black—both died. ama ese Ob i fe preserved. cab il) Mite. ni és one died. The other was a female “‘ no-white ”’ on right side. , Ll. 1 “no-white’’ Red male, one.side only. ,, IV. Contained 31 voung, the eyes in all with very imperfect and broken reticulation. , VI. 1 “ no-white ” Black, female, left side. One brood of 12 young. 1 “ no-white” Black, died. All the others with the reticulation imperfect. One brood of 7 young, 5 with imperfect reticulation. One brood of 32 young, all with imperfect reticulation. . The male was from Af,, the female from Df,. Brood I. 38 young. 1 “no-white” Black, died. Many with reticulation imperfect. Several Red, very pale colour. , Il. 2young. 1 Black “no-white” both sides—died. é INHERITANCE OF EYE-COLOUR IN GAMMARUS. 45 Another instance is that of Exp. 99 (p. 38), a Pure Black male from Bf, mated with a Recessive female, both with normal eyes. All their young, 86 in number, were also normal. In the F, generation the “ no- white ” and the “ part-white ” strains appeared in the offspring of a pair from Brood 7. This pair had three broods, the first brood of 6 died young. Of the second brood, 21 in all, 13 Black and 8 Red, only 7 survived, 3 Black males, one with the left eye affected (in this case 2 or 3 of the omma- tidia formed a little cluster apart from the ommateum). 4 Red survived, two normal and two “ part-white ”’ as figured (Fig. 7). (In the first brood from these Reds 3 out of the 4 young (F,) had normal eyes, the fourth had eyes like the male figured.) The third brood numbered 30, 20 Black and 10 Red, of these 6 survived, 4 Black and 2 Red, only one normal-eyed amongst them, a Black. Two of the other Blacks were “no-white” on both sides, and the remaining one was normal on the right side, but had a small cluster of ommatidia apart on the left side. Of the two Reds, one was ‘‘no-white ” on the left side, the other had the white reticulation partly lacking, i.e. partly “ no-white.” Many cases have occurred in which the white pigment (instead of being diminished or lacking) is present in excess. This appears to be always accompanied by a diminution of the coloured pigment of the retinular cells, the red, e.g., being hardly perceptible, even with a strong lens showing only as a very pale pink tint, instead of the vivid blood-red of the normal red eye. This variation has been noticed especially in the later generations of the inbred Recessives, and it is possible that another generation or two of inbreeding may produce the “ all-white” eye. Only a few “ all-whites”” have been recorded so far (Nov. 19, 1915). Two, a male hatched April 2, 1915, and a female hatched April 14, have appeared in the Pure Red Stock amongst the young from Brood 4, Exp. 5, Recessives (p. 27) (descendants of the fourth brood of female A of the original experiments, p. 22). The female came to maturity but died without mating. The male (Fig. 8) was mated with female B (Figs. 9 and 10), referred to below (a Hybrid with degenerate “white” eyes), and proved pure Red—the 5 young being normal-eyed, 2 Black and 3 Red. It died in moulting, November 19, 1915, without mating again. ‘Two other females from the same brood as the “ all-white” female extruded their young in the brood-bowl, 6 in number, all with very pale pink, almost ‘‘ white ” eyes. A curious instance of -the ‘‘ all-white” accompanied by degeneration of the eye was noted in the forty-second brood of M family, F, Hybrids (p. 31). This brood was extruded on June 1, 1915, and numbered 12 young, 7 Black, 1 Red, and 4 “ all-white ” eyes. These four proved to be 1 male and 3 females. The male mated with one of the females, eggs were 46 E. W. SEXTON AND M. B. WING. laid but thrown off, then the male died and was eaten. A Pure Black male was put in, mated with one of the females, but ate it after mating. By September 26 only the two females B and C were left. The “ all- white ” male from the Pure Red Stock with unpigmented perfectly formed eyes (Fig. 8) was put with them and mated at once with female B (Figs. 9 and 10), eggs were laid, and 5 young were extruded, on October 16, all with normal eyes, 2 Black and 3 Red. This result proved beyond doubt that female B was a true Hybrid and the male a true Recessive. The second female, C, was left with the same male, but as no mating had taken place by October 28, a Red male was added, mated, and the eggs were laid on November 4. The figures given of the eyes and eye-colours are all taken from living animals, for the colours alter so rapidly after death, that notes made on the colour in dead or preserved specimens are not of the slightest value. For instance, the white pigment disappears within an hour or two of death, and the red also fades out completely, though much more gradually. GENERAL NOTES. Breeding different generations together —Eight experiments were made with males of the F, generation and females of the F,: one with R. x H.; two with H.x R.; two with H. x H.; and three with H. P. In the first, the male was rather small, mated three times, and carried the female for 7, 6, and 6 days respectively with no results; female disappeared. In 2nd Kixp. the female was eaten; 3rd Exp., one brood of 26 young was hatched, 11 Black and 15 Red, the male died; 4th Exp., one brood of 6 young ; 5th Exp., eggs were laid, not hatched, male died; 6th Exp., same male as in the second experiment, one brood of 5 young, male died; 7th Exp., female laid eggs but died before they hatched; 8th Exp., four broods of 36, 17, 30, 30; male eaten. The results are not satisfactory, probably because of the difference in size. The females were large, and the males had only just reached maturity. When the animals are about the same size there is nothing to distinguish their matings from those of animals of the same generation. Fertiliiy.—A great variation in fertility has been noticed, not only in individuals, but often in all the members of any one brood. Some instances may be given in illustration from broods of the F, generation of the Recessives. As an example of infertility Brood 1 of Exp. 9, p. 27, may be taken. Ten voung were hatched, and most of them reached maturity, but after six months’ breeding they all perished without leaving a single descendant. Brood after brood of eggs were laid, but not a single young one was hatched. INHERITANCE OF EYE-COLOUR IN GAMMARUS. 47 Another brood, Exp. 5, Brood 4, kept under the same conditions as the one just mentioned and breeding during the same time had 132 young. In the following four months, March to July, 1915, 91 young were hatched. The next brood of the same experiment, Exp. 5, Brood 5, shows a curious variation. There were the same number of individuals as in the last, the same conditions, ete. After six months’ breeding only 2 young were hatched from all the eggs laid, but in the following three months, April to July, 1915, 90 young were hatched. For instances of fertility and infertility in individuals some of the F, animals may be taken. Sometimes an animal will mate several times with no results; the most striking case of this was the H. female of Exp. 39 (p. 36). Mated with a Black male, eggs were laid on September 12, 1914, carried for six days and then thrown off; eggs again on September 25 and again thrown off before hatching. The male was taken away, and another Black male put in: eggs laid on October 9 and thrown off; eggs again on October 23 and again thrown off. Then the female was left for a period without a male. On November 29 the male was put back, and eggs were laid, a large number, thrown off some days later; eggs laid on December 14, a large number, thrown off; eggs laid on January 3, 1915, all there on January 12, but on the 14th they were all thrown off except two, these were carried a day or two longer but not hatched. The male was taken away, and a Red male put in, which died on January 26 without any mating taking place. Then two more Red males were added —-one disappeared on February 8. The female laid eggs, very few, these were thrown off on February 11. The male was again changed. On February 17 eggs were laid, and from these 4 young were hatched on March 8. Eggs were laid on March 10 and 12 young hatched on April 3. A fresh brood laid on April 3, hatched out on April 23, 19 young. The male disappeared and another was put in. Eggs laid on June 1, very few in number. On June 9 the male ate the female. The seven males used in this experiment, 2 Black and 5 Red, were all healthy animals, which had already fertilised the eggs of other females. Numbers in Broods.—As a rule it is found that an exceptionally large brood of young is followed by a very small brood, or by the omission of one period of sexual activity, but in several cases the animals had a series of large broods, the highest numbers recorded in two succeeding broods being: In Exp. 11 (R. 2 mated with H. 3), 42 in the brood and (mated directly after with another H. 3, Exp. 20) 44 in the next; in Exp. 51 (H. 9 x R. 3), 40 and (mated then with H. 3, Exp. 106) 52, the largest number in a brood yet recorded; Exps. 60, 68, and 104 (H. 3 x R. &) had 47 and 31, 30 and 48, and 40 and 43 respectively, and Exps. 70 and 48 E. W. SEXTON AND M. B. WING. 71(P.2& R. 3, and H. 2x R. 3) had 43 and 23, and 41 and 41 respectively, all except Exp. 70 being Hybrid Black and Recessive matings. Different rate of development.—There is often a marked difference in the rate of development of individuals in the same brood, and also of broods from the same pair. For example, in Exp. 85 (p. 38) some members of a brood hatched on January 6, 1915, were mature in March, the others not till June. Many instances like this were noted. In Exp. 99, Brood V took four months to reach maturity ; Brood VI, seven months; while Brood VII was mature in two months, and the animals were then much larger than many of the broods hatched three months earlier. It was found that Bacteria greatly retarded growth; in one case a female took eight months to become mature, and was then only about half the normal size. SUMMARY. 1. Twenty-one thousand, five hundred and fourteen (21,514) amphipods of the species Gammarus chevreuxi Sexton have been examined for eye- colour, 21,302 referred to in this paper, and 212 in other experiments, not included. 2. The normal eye-colour of this species is black, with a superficial reticulation of opaque white pigment. 3. The pigmentation of the eye is very variable within limits. Eyes have been observed either partially or entirely lacking in the coloured pigment of the retinular cells, or with either a partial or entire lack, or else an excess of the opaque white pigment. 6 4. The red strain appears to have arisen as a “ sport” in the second generation of offspring of the first animals captured. No red-eyed animals have yet been found in natural conditions, although many thousands have been brought in from time to time and examined. Those counted for the purpose while the work for this paper was in progress numbered 8697, but this figure does not include the many thousands previously observed. Experiments have been made repeatedly with a view of getting the Red strain again from the Pure Black, but with no success. 5. The Red eye-colour is not a sex-limited character ; about as many males as females come to maturity. 4248 red-eyed animals have been examined, 4175 referred to in the paper, and 73 in control experiments. 6. The inheritance of the coloured pigment of the eye follows the Mendelian law— Black is dominant and Red recessive. The dominants are divided into Pure Black and Impure or Hybrid Black. INHERITANCE OF EYE-COLOUR IN GAMMARUS. 49 7. The Pure Dominants and the Recessives breed true through all generations. 8. The crosses which have been made and the young hatched from them are as follows :— Pure Black x Recessive.—3779 black-eyed young ; 3746 in paper, 33 in control experiments. Hybrid Black x Recessive.—4255 young, of which 2176 were black-eyed and 2079 red-eyed. Those referred to in the paper numbered 4189, 2138 Black and 2051 Red, the others came from other experiments in the F, generation—-not included. Pure Black x Pure Black.—All black-eyed young, 1715 in number. Pure Black x Hybrid Black.—All black-eyed young, 379 in number. Hybrid Black « Hybrid Black.—4393 young, of which 3327 were black- eyed and 1066 red-eyed. Those referred to in the paper numbered 4302, 3259 Black and 1043 Red—the other 91, being from the F, experiments, not included here. 9. The absence or diminution of the white pigment seems peculiar to some broods. The “ no-white”’ eye appeared in the second generation of offspring of Pure Black animals brought in from the ditches. The indi- viduals affected in this way are more difficult to rear than the others, and, so far, attempts to breed them have not been successful. 10. The absence of the coloured pigment and degeneration of the eye occurred also in the F, generation—in this case from Hybrid Black animals. 11. The absence of the coloured pigment in perfectly formed eyes, the “ all-white” eye, occurred in the Recessives. A great diminution of the red pigment has also been observed, particularly in the F, generation of the inbred Recessives. 12. The absence of the coloured pigment in part of the eye, the “ par¢- white” eye, was observed in the first generation of offspring of Pure Blacks brought in from the ditches. It has been noted several times in both black and red eyes of specimens bred in the Laboratory, but only once in fresh-captured material. This case was a male, with one eye affected. 13. About as many males as females survive to maturity. 14. The breeding together of animals from different generations gives the same results as regards proportions of colours as the breeding together in the same generation. NEW SERIES.—VOL. XI. NO. 1. MARCH, 1916. D 50 ¥ia. Fia. Fic. Fic. Fic. Fic. Fre. Fic. Fie. Fie. E. W. SEXTON AND M. B. WING. EXPLANATION OF PLATE I. 1.— Pure Black eye. Female from Brood 1 of Exp. 118 (p. 41). Extruded June 9. Mated with Red male, first brood hatched Aug. 26 numbering 14; five more broods, 19, 31, 24, 41, and 36 respectively, all black-eyed. Figured Oct. 29, 1915, a few hours before moulting. » 58. 2.—Hybrid Black eye. Female from Brood 7 of Exp. 105b (p. 41). Extruded April 29, figured Nov. 24, 1915. Mated with H. male, one brood of 13, 10 Black and 3 Red. x 58. 3.—Red eye. Large male from Recessive stock. Figured Nov. 5, 1915, two days before moulting; examined after moulting but no increase of ommatidia seen. xX 58, 4.—Right eye of young Hybrid from H.R. cross. Extruded Oct. 22, figured Oct. 25, 1915; the white pigment was then much more solid in appearance than when newly hatched. » 75. Right eye of young Red from Recessive stock. Extruded Oct. 21, 1915, and figured three hours after extrusion. » 75. 5. 6.—* No-white” eye. Young male from the second generation of Pure Blacks (p. 25). Figured Nov. 23, 1915. x 58. 7.—* Part-white’’ eye. Male. F, generation from P. x R. cross (see p. 45). Ex- truded June 15. Figured Nov. 2, 1915. x 58. 8.—“ All-white”’ eye. Male from inbred Recessive stock (see p. 45). Extruded April 2, died in moulting and figured Nov. 19, 1915. x 58. 9.—‘ All-white”’ degenerate eye, right side. Female B. F, generation from P. R. cross (see p. 46). Extruded June 1, figured Nov. 16, 1915. x 58. 10.—*‘ All-white ” degenerate eye, left side, from Female B. Figured Nov. 16. x 58. Journ. Mar. Brox. Assoc. Vou. XI PLaTE | ow so08 & J "soe @e 0¢ wv Oy 9% OGe %®e6 G %q Se ooe% a © goec’, 1g9P Co PATH 3490 Oe o.%@e € > 4°00 @' 12,0000 Veoee- @",gee0 See: 1.® o%ef ae 4 OQ 2 3 ! go Stet 4 Oe to%oc%e ty o,*@ i@* rye Ageee, o* Yee, gate a < a hgh S, ae 6, %e ) 4 5 We “ e 7 i) 8 0 E. W. Sexton del. Notes on the Life History of Anaphia petiolata (Kroyer). By Marie V. Lebour, M.Sc., Assistant Lecturer in Zoology, Leeds University. Temporary Naturalist at the Plymouth Laboratory. With Figures 1 to 3 in the Text. In the early summer of 1915 it was noticed that many medusz brought in with the tow-nettings contained larval Pycnogonids in the manubrium and at the junction of manubrium and stomach. The medusv specially noticed to contain them were Obelia sp., Cosmetira pilosella, Turris pileata, Stomotoca dinema and Phialidiwn hemisphericum. By far the greater number were in Obelia, although many were in Phialidium hemisphericum and Cosmetira pilosella. They were extremely abundant in June, after that became scarcer, and finally disappeared by October. On examination they were seen to be larval stages of Anaphia petiolata* (Kroyer), a Pyecnogonid common in Plymouth Sound. The older larvee sometimes were seen to cast their skins, so that the species could be easily recognised, although the fourth pair of walking legs were not fully developed. This is evidently the species described by Dogiel (1913) as Anoplodactylus pygmeus, the life history of which he traces from its first entry into the Obelia hydroid to the older stages when it is ready to leave its host. The form he refers to as Anoplodactylus petiolatus occurring in cysts in Coryne with Phoxichilidium femoratum must be some other species, as his figures prove clearly that it differs from A. pygmeus, and also the colour is totally different (a bright pink, while the present form ‘is a pale yellow). Dogiel believes he has proved that Anoplodactylus petiolatus and A. pygmeus are different species from the difference in their life histories, and it is evident that he is dealing with two different species, but his 4. petiolatus cannot be the same as our form, which is certainly identical with his A. pygmaeus, and shows that Sars (1891) and Norman (1894) were right in regarding A. pygmaeus as the young form of A. petiolatus (Kroyer). * This is a synonym of Anoplodactylus petiolatus (Kroyer), See Norman, 1908, p. 202. a) MARIE V. LEBOUR. Dogiel’s account of the larval stages of A. pygmeus, together with the present discovery of the older larvee in medusx, shows a most interesting life history. According to him the very young larva hatches out of the egg (which contains very little yolk), leaves the protection of the father, and crawls on to the Obelia hydroid. In this early stage it has three appendages, the first the chelee, the second and third with long thread- like ends which are used for attachment to the father directly after hatching. It immediately begins to burrow into one of the hydroid polyps, and once settled down there undergoes a metamorphosis, the second and third appendages atrophy, and three pair of walking legs develop. After several moults older larvae appear, which are like the adults, except for the incompleteness of the last pair of walking legs, and these leave the hydroid and begin to live a free existence. The stages found in the medusz correspond to the larval stages after the second and third appendages have atrophied. The youngest stage seen corresponds with Dogiel’s Stage [IV with the three pair of walking legs indicated and the chelz well stretched out in front, which are used for clinging firmly to the host. Dogiel has called attention to the fact that many larve do not succeed in entering the polyps, and have to undergo their development on and not in the hydroid, and now we find still another alternative for the larva. 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MAY JUNE JULY AUG, SEPT. 1915 1916 Fic. 1.—Curve of Skelctonema costatum, showing average number of individuals in 50 ec. for each month. season of maximum number agrees. As Lohmann observed at Kiel, so here, there are several amcebe to be found in the plankton. Ours are of three kinds, one of which is fairly common. With him Flagellata are much more numerous than with us, except Pheocystis, which is so abundant here in May and June that it interferes with everything, clogging up all the nets. Infusoria Lohmann finds numerous, and there are numerous species of them here, but they are not found in large numbers with the exception of the Tintinnoidea. The smaller forms, such as Laboea species 138 MARIE V. LEBOUR. and Strombidium caudatum, very easily collapse and destroy themselves ina moment. Tvarina fusus we find at a larger maximum than at Kiel. Most of the new species, both of the Peridiniales and Infusoria found in the plankton by Lohmann, are present here if not in such large quantities; thus we have Amphidinium crassum, Pouchetia parva, Cochlodinium pellucidum, Laboea strobila, and many other species hitherto not known from British seas. The diatoms, although usually in less numbers than Lohmann’s, are in some cases more. Nearly all his diatom numbers are, however, from filter examinations, therefore not exactly comparable. One fact which is striking is the relative regularity of the yearly curve of certain species, instead of their showing a marked seasonal distribution. This we find to be the case with Thalassvothrix nitzschioides, which is present at Kiel practically all the year round whilst with us it is a pronouncedly winter form. The same is true with most of the Coscinodiscus species which also are winter forms here. This is perhaps to be explained by Gough’s theory of the distribution of neritic diatoms which he found occurred at certain definite times only in places near the ocean, but stayed all the year round in suitable localities far removed from it. We find much the same seasons for the above diatoms at Port Erin as we have at Plymouth (see Herdman and Scott, 1908-15). For comparison I have taken from Lohmann’s tables certain species with their maximum number in 100 litres and put side by side of these the Plymouth records of the same species in the same amount calculated from the number in 50 cc. The month of maximum is also recorded. It will be seen that in most cases his numbers are higher, in a few instances much higher, but in three cases the Plymouth numbers are higher. Species. Kiel. a po Plymouth. Bs uy Paralia suleata . : 77,000 Nov. — 1,000,000 Nov. Skeletonema costatum . 778,000,000 June 25,000,000 April Guinardia flaccida 360,000 May 20,000 Sept. Asterionella . 1,800,000 Dee. 3,260,000 July (japonica) Prorocentrum macans 5,100,000 Aug. 128,000 Sept. Glenodinium bipes —. 2,100,000 May 12,000 Aug. Ceratium fusus . : 300,000 Sept. 12.000 Aug. P. armata Pouchetia parva. ; 50,000 Sept. 30,000 June Tiarina fusus . 11,000 Oct. 14,000 Aug. As will be seen, the maxima here agree in most cases in being in the spring or autumn. As has been stated above, however, there are several THE MICROPLANKTON OF PLYMOUTH SOUND. 139 species which do not agree; for instance, Coscinodiscus Grani has a maximum at Kiel in August, whereas I found it confined to the period from November to April, when it is fairly evenly distributed. The maximum of Prorocentrum micans in August or September seems to be well established. Ostenfeld (1913) is here also in agreement. Ceratiwin fusus also has its maximum at this time, and Pyrocystis lunula, which at Plymouth is only recorded in these months. However, I find that in many cases species having a spring maximum at Kiel have it here in the summer. A comparison of the present results, with those of Gran (1912) is difficult as his are only for the month of May and from so many stations at various localities and many different depths. . However, if we take the Dutch results from the south-western part of the North Sea, which is the nearest to us of all the localities he makes use of, and compare them with the present records for the month of May only, we find the comparison is not without interest. Gran used the centrifuge entirely and the samples were all preserved. He usually took 50 cc. of the sample and calculated from it the number of individuals ina litre. Except in certain cases mentioned below, the numbers are not extremely different. Thus we find the species of Biddulphia present in very small numbers (only B. sinensis at Plymouth), a large number of several Chetoceras species in both (12 species with him, 8 with us). However, whereas there C. decipiens and debile are the prevailing forms (maximum numbers 11,500 and 6,500 per litre respectively) the prevailing forms here are C. curvisetum (maximum number 39,900 per litre) and C. pseudocrinitum (maximum number 30,000 per litre). A large number of resting spores of Chetoceras species are recorded by Gran and also by Lohmann. They were not recognised and therefore not recorded in the present paper. Lauderia borealis (Gran’s maximum 2,180 per htre) with us is more abundant (21,580 per litre). Paralia sulcata (Gran’s maximum 7,180 per litre at 30 m.), with us 700 per litre at 7 fathoms. Rhizosolenia species fairly abundant : Dutch records. Plymouth records, R. alata . : 72.800: (aes) 120 surface R. semispina . . 160 (20 m.) 500° 5.f. R. Shrubsoler . . 480 (10 m.) 1600: dif. R. Stolterfothir . . 8,360 (50 m.) 760 surface Thalassiosira gravida (Gran’s maximum 1,7€0 per litre, Plymouth 6,320 per litre). Nitzschia delicatissima much more abundant at Plymouth, N utzschia closterium more abundant in the Dutch records. Of the Silico- 140 MARIE V. LEBOUR. flagellata Dictyocha fibula and Distephanus speculum are few in numbers as in our records, also the individual numbers of the Peridiniales which are often represented by single examples or by twos and threes. It is, however, among the Infusoria that a great difference is seen, for whereas my own records seldom show more than a few specimens in each sample, the small Infusoria are in fairly large numbers in the Dutch records, especially the species of Laboea, which sometimes reach five figures per litre. The Metazoa agree with my records in only being represented by very few individuals. Herdman’s (1908-15) quantitative estimates of the plankton for Port Erin and the south end of the Isle of Man are taken from the tow nets only. These are only comparable with the present records to a certain degree, but some facts stand out as of special interest. Here we find the large spring and smaller autumn maximum for the diatoms, the seasonal distribution of certain genera and their maxima, Rhizosolenia species in June; Chetoceras, Thalassiosira and Lauderia in April and May ; Chetoceras and Lauderia again in September and October; all these agree well with our records. The species of Beddulphia agree in being almost entirely absent from June to August and being much the most common from November to May. Coscinodiscus again agrees in being absent in the summer and early autumn and common in winter and early spring, Rhizosolenia species being only common in summer. Thalas- svosira has its maximum in May both at Port Erin and Plymouth, with a shght second maximum at Plymouth in 1916. Gwinardia is slightly earlier at Port Erin than at Plymouth. Lauderia with a large spring and small autumn maximum at both places, and the same with Chetoceras. Asterionella japonica appeared in large quantities in May, 1913, at Port Erin. At Plymouth it has a maximum in July and is present on and off from April to January, common through July and August. Apparently this species is irregular in its appearances, as Gough records it from Plymouth as ec in May. The numbers of Peridiniales at Port Erin are enormous compared with the present results ; Ceratiwm species and the larger Peridinium species forming the basis of the Port Erin records. However, we are in agreement in finding the Peridiniales maximum to occur very shortly after the diatom maximum and the maximum a single one which is only in the summer, May usually at Port Erin, June this year for Plymouth, when the curve shows a conspicuous hump, gradually dwindling in September, after which month very few are present. The smaller Peridiniales are not taken into account in the Port Erin reports, and the Gymnodiniacee, which turn out to be abundant, are necessarily not noticed as they come through the nets. The same applies to the other small unicellular organisms. THE MICROPLANKTON OF PLYMOUTH SOUND, 141 THE DIATOMS. In estimating the diatoms, we find they fall naturally into two groups ; the first and most important includes the species beginning about April and usually ending about September, the second including those having their maximum in the winter or spring and extending from September 2500 200 Sa 1500; 1000 900 800 700 600 500 400 300 200; — | SEP, OCi.. NOV, "DEC, JAN, FEB: MAP APR, MAY JUNE) JUIEY AUGS SEPT: 1915 1916 Fic. 2,—Curve showing average number of diatoms in 50 ce. for each month. 10G or October to the end of March or April and May. In September these groups sometimes overlap, but the two large general maxima occur about April and from August to October, the diatoms of the first group thus being mainly responsible for both the spring and autumn maxima. The curve here given (Fig. 2) shows the average number of diatoms in 50 ce. monthly throughout the year. The largest maximum is in April, although May comes very near. The autumn maximum here this year is 142 ; MARIE V. LEBOUR. early and occurs in August. It is very nearly as big as the spring maxi- mum. Also in the curve there is another maximum in October, 1915, after which the numbers are very low, until they suddenly rise enormously in April. The October maximum is possibly the ordinary autumn maximum occurring later in 1915 than in 1916. For the rise in April Skeletonema costatum is almost wholly responsible ; in May Chetoceras species are mainly responsible, together with Nutzschia delicatissima, Thalassvosira gravida and helped by Rhizosolenia species and Lauderia borealis. For the August maximum Chetoceras again is to the fore with Asterionella japonica, Mastigloia at times in numbers, Rhizosolenia species and Nitzschia species. The rise in October, 1915, is due to Mastigloia, Cheetoceras, Lithodesmium undulatum and Skeletonema costatum. The diatoms of the first or spring and summer group include the genera Asterionella, Chetoceras, Lauderia, Nitzschia, Rhizosolenia and Thalassio- sira; those of the autumn and winter group include Biddulphia, Coscino- discus, Paralia, Streptotheca and Thalassiothrix. One of the most important diatoms is Skeletonema costatum, which, although occurring practically all the year round, yet has certain times of total disappearance for short periods. It cannot be placed in either of the above-mentioned groups as it extends over both. We find this year the genera Biddulphia and Coscinodiscus disappear suddenly and do not continue in small numbers through the summer, as is the case generally at Port Erin. Gough, however, has recorded Bid- dulphia mobiliensis in June and August from Plymouth, so it must occasionally be present ; also Coscinodiscus species very rarely. Paralia and Thalassiothriz are essentially winter forms here, the latter stopping abruptly in the sprmg and the former being much commoner in the winter, although occurring throughout the year. The records of Bygrave and Gough are here also in agreement. Several important species have only one maximum in the year. Monthly curves show a gradual decrease from it. Asterionella japonica (July), Rhizosolenia Stolterfothi (May), R. alata (June), R. Shrubsoler (May), Rh. hebetata f. semaspina (May), R. setigera (August), are examples ; also Biddulphia species and Coscinodiscus species (autumn to spring) the curves of which could not be exactly determined because of their presence only sparingly in the water samples. The following are some of the most important species which have two maxima: the larger in April, May or June, usually very much exceeding the second in August or September : Skeletonema costatum (April and September), Chetoceras curvisetum (May and September), Lauderia borealis (April and August), Thalassvosira gravida (May and September). These results agree roughly very well with the previous records for Plymouth by Gough and Bygrave. THE MICROPLANKTON OF PLYMOUTH SOUND. 143 Large masses of a species of Mastigloia in a gelatinous sheath some- times occur at intervals and swell the number of diatoms largely. In these cases they are usually so numerous that I have estimated them in 10 ce. instead of 50; I have also done this with other species when very numerous. Table IL shows the average number of diatoms in 1 cc. for each month. In the following details of the species the classification of ‘* Nordisches Plankton,” Vol. III, Gran (1905) is used. (1) Melosira Borreri Grey. Not common. In water samples, October to March. (2) Paralia suleata (Ehr.). Occurs almost all the year round in small numbers, but is essentially a winter species. Common from October to April with a maximum in November, then dwindles and picks up again in August. Nearly always goes through the nets.. More frequent at 5 and 7 fathoms although common some- times at the surface. Belongs, properly speaking, to the bottom but very often comes up to be a true member of the plankton. (3) Skeletonema costatum (Grey.). Very common for nearly the whole year, but has periods of disappearance. Rare in December and part of January, June and July. Maximum of 250 per ce. in April, when it helps largely in making the spring diatom maximum. Very numerous in August, September and October. A smaller second maximum in August, and in October, 1915, a still smaller one. Lohmann considers Skeletonema costatum the most important diatom at Kiel, where in June it reached a maximum of 780,000,000 per 100 litres. He finds it prefers water of 10 m. depth. Gran (19126) shows it likes surface water, and I have found that although common in all three depths it is usually commonest in the surface samples and its maximum of 12,500 in 50 cc. is from the surface. This is one of the most important of the plankton diatoms at Plymouth, but passes through the net in quantity. (4) Thalassiosira gravida Cleve. This is the only species of the genus found commonly in the water samples. It is abundant from the end of March to the middle of September with an interval of scarcity in July and August. May and June are the months given by Herdman for the maximum of the genus at Port Erin, which agrees well with us. It occurs at all depths, but its maxi- mum in May of 316 in 50 ce. is from the surface. ~ (5) T. Nordenskioldii Cleve. Not very common, occurring at intervals. Frequent in May. 144 MARIE V. LEBOUR. (6) 7’. decipiens (Grun.). Rare. (7) 7. subtilis (Ostenf.). This little species with its surrounding matrix occurred only rarely in 1916, although it was frequently noticed in 1915. (8) T. condensata (Cleve). Very rare. (9) Lauderia borealis Gran. An important part of the plankton from May to September, with intervals of scarcity. Helps largely in forming both diatom maxima. Rare from late autumn to early spring. Maximum in May. Its seasonal distribution agrees with Herdman’s records for Port Erin. At all depths, but largest numbers at the surface. Maximum of 1,079 in 50 ec. in May from the surface. (10) Leptocylindrus danicus Cleve. Fairly common from May throughout the summer, at other times very rare. CULO CZ Fic. 3.—Leptocylindrus sp. x 700. (11) L. sp. (Fig. 3). A small species which is like L. minimus Gran (1912), but never twisted as he describes; occurs fairly commonly in the summer plankton. There are seldom more than two cells in a chain and these are always quite straight. The two chroma- tophores, size and form agree with Gran’s species. (12) Guinardia flaccida (Castr.). Common at intervals from April to September, with a maximum in July. More common in the very fine tow nettings than in the water samples. The large numbers occurring at Port Erin in May and June (maximum in June) are noticeable. (13) Hyalodiscus stelliger Bail. Fairly common from October to February ; a winter species. At other times rare. Genus Coscinopiscus Ehr. All the species of Coscinodiscus we have found practically absent during the summer, which agrees well with Port Erin; although they continue through the year there except sometimes for one month, they are in very much smaller numbers through the summer. From September to May they occur at times abundantly and are common in the very fine tow nettings. THE MICROPLANKTON OF PLYMOUTH SOUND. 145 (14) Coscinodiscus excentricus Khr. Common from September to May. (15) C. radiatus Ehr. Common from September to May. C. excentricus and C. radiatus are the most abundant species. (16) C. sub-bulliens Jérg. Only noticed from September to December, Not very common. (17) C. Granw Gough. Begins in November and remains till April. Sometimes common in December, January and February. (18) Actinocyclus Ehrenberg: Ralfs. In tow nettings only. Rare. Sep tember. (19) Actinoptychus undulatus (Bail.). From the middle of September to the end of April, never very abundant, more frequent in tow nettings than in the water samples. Not seen at all in the summer. Genus RHIzOSOLENIA (Khr.) Brightw. With the exception of R. robusta which is the only winter form all the species of Rhizosolenia are markedly summer forms; beginning to be abundant in May they continue common until the end of September at all depths. If we compare this with the Port Erin records .we find it agrees well except for the fact that at Port Erin there are very few present in August. The curve (Fig. 4), giving the distribution of the various species, shows R. Stolterfothii as much the most abundant with a big maximum in June. As mentioned above, however, R. Shrubsoler occurred in enormous numbers in June in the tow nets, of a large size, and was not adequately represented in the water samples. The maximum of the species on the curve ought to rise very much higher. I find that R. Shrubsole: and Stolterfothi run together to a great extent, although Shrubsolec almost disappears in July, whilst Stolterfothic continues common well into September. The genus is hardly represented at all from November to April. Its absence being very striking, &. alata follows R. Stolterfothi closely, although it is not so common. &. hebetata form semispina, has its maximum in May. AR. setigera is later, beginning in June and ending in September, with a maximum in August; thus it is later and remains less time than any of the others. All the species are abundant in the tow nets. 146 MARIE V. LEBOUR. (20) Rhizosolenra Siolterfothii H. Perag. Perhaps the commonest of the Rhizosolenia species. Very common from May to September, with a maximum in June; disappears entirely in December. 1500 1400 1300 ~ SN Soe | WZ ss 3 re ‘ ao: XP | & < Oy SEPT. OCT. NOV. DEC. JAN. ~ FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. 1915 1916 Fic, 4.—Curve showing average number of Rhizosolenia Shrubsolei, Stolterfothii, alata, setigera, and hebetata f. semispina in 1000 ce. for each month. In the tow nettings it occurs in long spirals with many cells in each. In the water samples, however, these are broken up and only a few cells cling together, and many single cells are present. THE MICROPLANKTON OF PLYMOUTH SOUND. 147 (21) R. robusta Norman. This is the only winter Rhizosolenia here. It begins in November and, although never common, continues till April. Chiefly in the tow nettings. Very seldom in the water samples. (22) R. Shrubsolei Cleve. Very common in May till the end of June, then dwindles and is rare in August, almost absent in the winter. (23) R. setigera Brightw. Very common in July and August, when it seems to take the place of R. Shrubsolev; rare in spring and autumn and almost absent in winter. (24) R. hebetata (Bail.) f. semispina (Hensen). Begins in May and is very common till the middle of August, after that is rare and disappears entirely in the winter. (25) R. alata Brightw. Begins to be common in June and continues till August, after that is only rarely found, although a few stragglers are present throughout the year. (26) Corethron criophilum Castr. Most frequent in October but never common. Absent for nearly the whole summer. Genus CH&#TOCERAS Ehr. Although scattered throughout the year, all the species occur chiefly in the spring, summer and early autumn, forming an important portion of both maxima. A very large maximum in May (Fig. 5) agrees with the Port Erin records, but the autumn maximum in August is small, not amounting to more numbers than in March. This rise in March is partly due to numbers of C. densum, the maximum number of that species in the water samples. This species, however, is large and, like C. boreale, does not get much into the water samples. Chetoceras curvisetum, which is much the commonest species found, shows two well- marked maxima, a large spring and a small autumn maximum, these agreeing with the Port Erin records for the genus. The fact that on several days in early autumn no Chetoceras species were seen in the water samples brings the average for the month down. (27) Chetoceras densum Cleve. Frequent in the tow nettings, but too large to be found much in the water samples. Present most of the year except at times in the summer. (28) C. convolutum Castr. From spring to autumn, sometimes abundant (29) C. danicum Cleve. Rare, at intervals through the vear 148 MARIE V. LEBOUR. (30) C. boreale Bail. Chiefly in two nettings, Occasionally in spring and early autumn. (31) C. decipiens Cleve. Fairly common in spring and summer. rare in autumn and winter. (32) C. teres Cleve. Chiefly in February and March, common in March. (33) C. contortum Schiitt. Occasionally in July, August and September. (34) C. didymum Ehr. Begins in February and continues through the spring and summer until October. Very common in August. 500 CHAETOCERAS SPECIES 400 300 200 100; SEPT. OCT. NOV. DEC. JAN, FEB. MAR. APR. MAY JUNE JULY AUG. SEPT 1915 1916 Fic. 5.—Curve showing the average number of Chetoceras in 50 cc. for each month, (35) C. constrictum Gran. One of the commonest species from July to the end of September with its maximum in May when it suddenly appeared and disappeared. Resting spores noticed commonly in August forming in the chains. At all depths, but the largest numbers nearly always at the surface. C. Willec Gran. Rare from June to October. C. breve Schiitt. Rare in August. This is recorded often by Gough. C. laciniosum Schiitt. Occasionally from June to October. C. diadema (Ehr.). Only seen once in August. C. pseudocrinitum Ostenf. Common in May and June, at other times rare. At all depths. (41) C. curvisetum Cleve. The commonest species of Chetoceras : begin- ning in March it continues throughout the summer till the middle of September, Maximum of 37 per ce. at the end of May. This is certainly the most important species of Chetoceras here and helps greatly to swell the diatom maximum both in May and August. Largest number at the surface, although it occurs at all depths. THE MICROPLANKTON OF PLYMOUTH SOUND. 149 (42) OC. debile Cleve. Not very common, May and June. (43) Cheetoceras spp. Species which could not be identified were common in July and August. (44) Eucampia zoodiacus Ehr. Occasionally from May to October. (45) Streptotheca thamensis Shrubs. Common from September to April, otherwise rarely seen. More frequent in tow nettings than in water samples. (46) Cerataulina Bergont H. Perag. Fairly common in May and June. Genus BrpDULPHIA Gray. The Biddulphia species are practically confined to the autumn, winter and early spring, being almost entirely absent in the summer. This agrees fairly well with the Port Erin records, although there, in small numbers only, they are found in the summer. At any rate they may be regarded as winter, or early spring, and autumn forms. B. mobiliensis, regia and sinensis arc all common in the early spring, winter and autumn. Whether B. regia and sinensis should be regarded as good species is a matter discussed at length by Herdman (1912), who has shown that intermediate forms are to be found and has figured forms from Port Erin which appear to be half B.-senensis and _ half B. regia or mobiliensis, his final decision being that they are probably all the same species. He therefore regards B. sinensis and B. regia as distinct forms of B. mobiliensis. There seems to be no doubt about the sudden appearance of the exotic species B. sinensis in numbers at Port Erin in November, 1909, and also that it suddenly appeared at the mouth of the Elbe in 1903, as 1s shown by Ostenfeld (1908) : having spread from the mouth of the Elbe into various places including the North-EHast of Scotland it was then found on the Belgian coast, Ostenfeld accounting for its presence there by imagining a reversal of the usual north-going current. Its first appearance at the mouth of the Elbe Ostenfeld thinks is probably due to its being taken there by some ship. In 1908 he predicted its discovery in the Channel, as up to that time it had not been found to occur there. In order to ascertain whether it was present in Plymouth in former years (it certainly is common here now) I examined a large number of old tow nettings mostly from the West Channel, Plymouth, and all from this district. Beginning: NEW SERIES.—VOL. XI. NO. 2. MAY, 1917. L 150 MARIE. V. LEBOUR. in 1897 I searched through samples of various dates, particularly autumn, winter and spring, without finding any trace of B. sinensis until October, 1909, when it suddenly became abun- dant and continued so within the limits of its seasonal range as is shown in these records until the present time. It is. very distinct and easily recognised and I find it hard to believe it is not a true species distinct from mobiliensis and regia. It occurs with them and is easily distinguished from them, and this year continues to stay longer than the others. The fact also, quoted by Herdman, that Dr. Allen and Mr. Nelson grew cultures of all three forms, which bred true for a year is strong evidence in favour of their being separate species. In some samples taken by Dr. Garstang in 1897 P. mobiliensis and regia were common, U lic, 6.—Varieties of Biddulphia regia. x 60. and amongst these I found an occasional specimen which showed an approach to sinensis. The figures (Fig. 6) were drawn with the camera lucida, and are very like some of Herdman’s figures. Although, however, one end is decidedly like sinensis and the cell is elongated (probably soon going to divide), I think these are varieties of regia only and not true sinensis species. It seems from this that occasionally B. regia can show varieties approaching B. sinensis and perhaps this is the explanation of Herdman’s mixed forms. If this explanation be correct we thus find B. sinensis appearing at Plymouth suddenly in October, 1909, and at Port Krin in November of the same year. The difficulty as to its origin is still a puzzle. (47) Biddulphia mobiliensis (Bail.) Grun. Begins to be abundant in the midd’e of November, keeping up its numbers until the end of March, is scarce in April, finally disappearing at the end of the month, not to reappear until the middle of August and then only singly. (48) B. regia M. Schulze. Much the same as B. mobiliensis but not quite so abundant and disappears earlier. THE MICROPLANKTON OF PLYMOUTH SOUND. 151 (49) B. sinensis Grev. Not so abundant as the other two but fairly common, continues until the end of May. (50) B. favus (Ehr.) v. Heurck. Rare, February and April. (51) B. alternans (Bail.) v. Heurck. Rare, October and early spring. (52) Bellerechia malleus (Brightw.) v. Heurck. Rare, September. (53) Lithodesmium undulatum Ehr. Common from August to October, rare at other times. (54) Ditylium Brightwelli (West) Grun. Appears and disappeais peri- odically from January to September. In March and September very common in the tow nets. (55) Fragillaria sp. Sometimes present in long strings in summer. (56) Thalassiothrix nitzschioides Grun. Common from September to the end of April. A winter species In summer rare or entirely absent. (57) Asterionella yaponica Cleve. Important in the late summer. Occurs in single groups rarely at intervals from October to the end of June, then suddenly becomes very common in July, rising to over 478 per cc. at the end of the month, abundant in August and gradually dwindles through September. Present in the tow nettings as well as the water samples. This seems to be erratic in its appearance as Gough records it as cz. in April and May (as A. glacialis). The largest numbers occur at 5 and 7 fathoms, maximum at 5 fathoms. (58) A. Bleakeleyi W. Smith. Only occurred twice, November and December. (59) Lycmophora Lynbergi (Kiitz) Grun. Rare, at intervals through the year. (60) Grammatophora serpentina Khr. pellucidum . | = | 2 9 2 ) Sis. : : nae pee se Ik Me 5 so. Juv. 3 - Pouchetia armata laa” ] 2 Dinophysis acuminata. : gees) Other organisms | 5 FLAGELLATA. ‘““Nordisches Plankton,” Vol. 2. ~ Pheocystis 1s certainly by far the most important of the flagellates, which interferes enormously with the catches by blocking up the tow nets in the early summer and entangles in its gelatinous covering many diatoms and Peridiniales. It also serves as food for many of the plankton THE MICROPLANKTON OF PLYMOUTH SOUND. 155 organisms. I have recorded this species by colonies instead of cells, as it was practically impossible to count the latter. Halosphera viridis comes next in importance, its swarm spores occurring oftener in the water samples than the spheres themselves. The other flagellates occur sparingly but belong to the genera recorded by others from plankton and are almost entirely missed by the nets. Oxyrrhis marina I have placed with the Peridiniales ; this species and a small species of Carteria, although not often found in the water samples, multiply freely in cultures where they are often found. The numbers obtained for flagellates, with the exception of Phawocystis, are much smaller than Lohmann’s. (1) Pheocystis Pouchetii (Hariot) Lagerheim. Begins to be common in the middle of May and continues till the middle of June, interfering with all the tow nettings. Rare at other times. Not many colonies get into the water samples. The unidentified flagellates are chiefly swarm spores, probably of Phwocystis. (2) Dinobryon sp. (cf. balticum (Schiitt) Lemm.). Rare in August in the water samples in small colonies. A minute species. (3) Carteria sp. A very small species, rare, in water samples only. (4) Trochiscia Clevei Lemm. Rare, September and May. (5) Halosphera viridis Schmitz. Not uncommon from September to February. Very frequent in summer, especially the swarm spores, usually swimming freely but sometimes still in the parent sphere. COCOSPHAERALES. ‘* Nordisches Plankton,” Vol. 2. Pontosphera Huxleyi Lohmann. This is the only species found. It occurs occasionally in summer and in early autumn is sometimes abun- dant. Coccoliths of other species are very rarely seen. SILICOFLAGELLATA. ‘“‘Nordisches Plankton,” Vol. 2. The usual two species occur fairly commonly in the water samples. (1) Dictyocha fibula Ehr. From September to December and fron March to September. Commonest in September. (2) Distephanus speculum (Ehr.) Haeckel. Throughout the year, except in mid-winter, rather more abundant than Dictyocha. Commonest in September and October. 156 MARIE V. LEBOUR. RHIZOPODA. Amoebze, as Lohmann has pointed out, are not uncommon in the plankton. He records two forms, the largest number being 75,000 in 100 litres, but usually much less. He found July and August were the months in which they occur, and they were only found in depths of 5S and 10m. I find them from May to October, the greatest number being 140 in a litre. However, I have seen them much commoner than this in surface samples in 1915 when they were not counted. They occur in the surface water and also from 5 and 7 fathoms, the greatest number being from the surface. They are to be found either by examining the water directly or keeping it for a day or two, and, I think, there is no doubt that they are really free-living and do not come from harbouring in other animals. Three forms occur, one very much more common than the others. I have designated them A, Band C. Bis very common, A and C only occurred once each. A prominent feature of all is the form of the pseudopodia, which are all spiky when fully outstretched and in the forms A and B give the animal the appearance of a heliozoon. However, they were constantly observed to retract and were in reality perfectly soft although apparently firm. Form A (Fig. 9, A, 1,2 and 3), a very minute species, pale greenish brown with very long and exceedingly slender spine-lke pseudopodia. Greenish and brown granules inside. Circular even when the pseudo- podia are retracted. Form B (Fig. 9, B, 1, 2 and 3). Very common, larger than A, hyaline and perfectly colourless. Perhaps this is the same species as Lohmann’s No. 2. The pseudopodia stick out in regular spikes, much shorter and thicker than in A. These move in various ways and can be completely retracted. May to October. Maximum in May. Form C (Fig. 9, C, 1,2 and 3). A very clear and also perfectly colour- less form with a conspicuous central nucleus. At one end only isa small frill of spiky pseudopodia. These are usually in the same position, but are capable of being changed and appearing in another place. All these Amoebe are entirely lost by the nets. Heliozoa indet. Rare, only in November. Foranunifera indet., including Polystomella sp., occurred fairly fre- quently in the tow nets, especially in winter when they were stirred up from the bottom. 50, ») 500, Band Cx 3: Aux . 9.—Aniebe from the plankton. Fic. 158 MARIE V. LEBOUR. RADIOLARTA. * Nordisches Plankton,’ Vols. 3 and 17. (1) Acanthochiasma fusiforme Haeckel. At intervals throughout the year, sometimes abundant in June and October. (2) Lithomelissa setosa. Jorg. Rare, November and December. (3) Amphimelissa setosa Cleve. Rare, October to May. SUCTORIA. “ Nordisches Plankton,” Vol. 16. (1) Paracineta limbata Maup. Rare, November to January. (2) Acenita tuberosa Khy. v. Fraiponti (Fr.). Only once in October. (5) Ephelota crustaceorum Haller. Once in November on the legs of a Copepod. INFUSORIA. ** Nordisches Plankton,’ Vol. 15. The Tintinnoidea are much the most abundant of the Infusoria, as Lohmann found. However, a large number of small Infusoria are lost completely by the nets, and these are fairly common in the water samples. Many of them are exceedingly fragile and very easily destroyed. Prob- ably many of them are lost. Among those commonly found is a small species of Mesodinium allied to M. pulex, which is very difficult to count as it jumps about and collapses before it can be preserved. Species of Laboea are also common. Others unidentified are many and varied. Tintinnopsis ventricosa which is common in the water samples as wel] as the tow nettings has a maximum of 300 in a litre in June Lohmann found its maximum was 8800 in 100 litres. However, 7’. beroidea at Kiel had a maximum of 1,200,000 per 100 litres, while here its maximum number was 460 1m a litre. Several of the species originally described by Lohmann are found to occur here and some of Leegaard’s newly described species of Laboea and its allies. The abundance of these small Infusoria as found by Gran from the Dutch waters does not agree with our records. (1) Lachymaria sp. Only occurred once, water samples, May. (2) Coleps sp. A small species shaped like a flower-pot with square ends, water samples, rare, August. (3) Trarina fusus Cl. and L. Fairly common in August and September, rare in July and October, chiefly in water samples. THE MICROPLANKTON OF PLYMOUTH SOUND. 159 (1) Mesodirium sp. Common in water samples. (5) Nassula sp. Rare from May to August, water samples. (5) Strombidtum caudatum From. Rare in summer, water samples. Genus LABoEA Lohmann. The species of this genus, so far as I have seen, all have a yellow colour. They are common in- the summer but occur all through the year although very rare in winter. Some of the most delicate of the Infusoria. Never found in the tow nettings. (7) Laboea conica Lohm. The commonest species of the genus. Occurs fairly often through the summer, but never in large numbers. (8) L. strobila Lohm. Occasionally from July to November and also in January (9) L. acuminata Leegaard. Occasionally through the year, chiefly in May. (10) L. spiralis Leegaard. Rare, May and July. (11) L. sp. All through the year several unidentified species occurred, except for part of December and January. (12) Lohmanmiella oviformis Leegaard. Rare, only in August, water samples. (13) Huplotes vannus O.F.M. Once only in July, water samples. (14) #. sp. Rare, September, water samples. (15) Tintinnus subulatus Ehr. From July to October, not uncommon, most frequent in August. (16) Tintinnopsis berordea (Stein). Very common, both in tow nettings and water samples, but especially in the former early in November, middle of December, end of March and again through July and August : at other times not so frequent. Almost absent through October and the latter part of September. (17) 7. campanula (Khr.). Occasionally at intervals from August to March, not observed from April to July. Both in tow nettings and water samples. (18) 7. ventricosa Cl. and L. Common at intervals throughout the year. Commonest in September. In both tow nettings and water samples, but commonest in the water samples. 160 MARIE V. LEBOUR. (19) Citiarocyclis denticulata Fhr. Occasionally from Augus) to October. . J . . 1 This species is abundent close to the shore. (20) C. edentata Brendt. Once oaly in October, water samoles. (21) Infusoria indet. Chiefly in the summer and early autumn in numbers. THE METAZOA. The Metazoa in the water samples being negligible the following is an account of the tow nettings examined as described above through the same period as the water samples and from the same locality. CQLENTERATA. The medusee are chiefly confined to the coarse and medium tow nets. Beginning at the end of January with Phialidium hemisphericum they continue for the rest of the year until nearly the end of November when they are absent for the winter. Ctenophores and Siphonophores repre- sented chiefly by Pleurobrachia pileus and Muggiea atlantica are common in the summer, although Pleurobrachia was not so numerous as usual this year, possibly owing to the April storms and the coldness of May and June. The medusee are specially interesting because they carry other animals parasitically and thus serve as effective transports. Those chiefly so utilised are Cosmetira pilosella, Phialidium hemisphericum, Obelia sp., Turris pileata and Stomotoca dinema ; perhaps the species most frequently so used, and necessarily so as they are the commonest, are Phialidium hemisphericum and Obelia sp. Phialidium serves as host for larval trematodes, larval pycnogonids and Jarval Peachia. Obelia has not been noticed as a host for Peachia larve, probably because it is too heavy to be ‘arried by so small a medusa. Cosmetira serves as host for all three, Turris pileata and Stomotoca dinema for larval trematodes. The trema- todes are always the late cercaria stage of Pharyngora bacillaus (Molin), which reaches maturity in the mackerel (Lebour, J.M.B.A., 1915). This occupies the manubrium and mesogloea. It is interesting in this con- nexion that KE. T. Browne (P.Z.S., 1896) notes that a species of cercaria infects the mesoglea of Phialidium temporarium (i.e. P. hemisphericum) in Valencia Harbour, and that Halcampa (i.e. Peachia larva) also selected this medusa, attaching itself to the generative organs. I find that Halcampa attaches itself to the medusa margin as well as the inside of the generative organs. The pycnogonid Anaphia petiolata Kroyer lives in the larval state tightly folded up in the manubrium of Phialidium, Obelia and Cosmetira (Lebour, J.M.B.A., 1915). (11) THE MICROPLANKTON OF PLYMOUTH SOUND. 16] ANTHOMEDUS&. “ The Meduse of the World,” Mayer. Steenstrupia rubra Forbes. Begins in April and is common till the middle of June when it disappears. Hybocodon prolifer L. Ag. Begins at the end of March, is common through April, very common in May up to the middle, then dwindles and disappears in the beginning of June. Sarsia prolifera Forbes. Rare, in June only. S. tuberosa Lesson. Once only in June. S. eximia Allman. Once only in September. Slabberia halterata Forbes. Once only early in September. Stomotoca dinema L. Ag. Begins in July, is common through the month, becomes less common and disappears in November. Turris pileata (Haeckel). Fairly common now and then in June, July and August, rare in September and October. Bougainvillia brittanica Forbes. Once only in June. Rathkea octopunctata Haeckel. Begins in the middle of February, one of the first ineduse to appear, becomes very common in April and the beginning of May, disappears in the middle of June. It, however, reappears in September as a single specimen. Willsia stella‘a } orbes. Once only at the end of August. LEPTOMEDUS2. Obelia sp. Meduse extremely abundant. Begins at the end of February, very common from May to October, leaves off at the end of November and is absent through December, January and most of February. Cosmetira pilosella Forbes. Begins in May, very common on and off from June to September. Clytia volubilis Lamouroux. Once only in April. Phialidium hemisphericum (Gron.). Perhaps the commonest of the meduse here. Begins at the end of January, is common from May to October and continues till the middle of November. Saphenia gracilis Forbes and Goods. Rare in May. On June 14th the nets were full of it and it was abundant once in August. 162 MARIE V. LEBOUR SEM .£OSTOME.E. (17) Chysaora sp. Once in November. (18) Aurelia sp. Ephyre. One on January 24th. Continues fairly commonly from February to the beginning of April, then stops. One occurred on September 6th. SIPHONOPHORA. (19) Muggiea ailantica J.T. Cunn. Once at the end of January, rare in February, but continues till September, when it is very common. CTENOPHORA. (20) Pleurobrachia pileus Fab. Fairly common, February to July, and from September to November, chiefly young forms. (21) Bolina infundibulum Fab. On June 14th the nets were full of it with Saphenia gracilis. In October, 1915, it was fairly common. (22) Bero? cucumis (Kab.). In October and November, 1915, and in- May to August, 1916, rare. ZOANTHARIA. (23) Arachnactis Bourne: Fowl. Larva of Cerranthus Lloyd Gesse. From March to June, common. (24) Peachia sp. larva (=Halcampa chrysanihellum (Peach) of Haddon), common, May and June to the middle of July, on meduse. PLATYHELMINTHES. Amongst these are some interesting larval trematodes which oceur in the free state, having been captured probably in the interval of changing hosts. Also two parasitic in meduse and in Sagitta, both of which eventually enter fish as their final host. (1) Pharyngora bacilaris (Molin). What I believe to be the free-swimming tailed cercaria of this species occurred once in fair numbers on January 28th, 1916. It is described in a separate paper (p. 201) of this Journal. The late cercaria without a tail is found parasitic in medusze and in Sagitta, besides being sometimes free in the sea at intervals throughout the year. Commonest in June. THE MICROPLANKTON OF PLYMOUTH SOUND. 163 (2) Derogenes varicus (O. F. Miill.). Occurs in Sagitta bipunctata in the late cercaria stage in June. Jn old material of previous years it is quite common. (3) Turbellarian indet. Occurred occasionally in August and November. NEMATODA. Unidentified trematodes occurred occasionally free in the autumn and winter; a larval Ascaris (described in another paper of this Journal, p. 201) is common in Sagitta bipunctata. ANNELIDA. K: J. Allen, “ Polycheeta of Plymouth and the South. Devon Coast, ete.,” JMB. As OTS. The annelids with the exception of Tomopteris and Autolytus are all larval forms. (1) Autolytus longiferiens De St. Joseph. Occurred once at the end of January with eggs, twice with eggs at the beginning of September, and one male. (2) A. rubropunctatus (Grube). Once in September, 1915, twice in November, once in August and twice in September, 1916, always with eggs, (3) A. pictus (Ehlers). Once in September and once in Noversber, 1915. Once in September, 1916, alwavs with eggs. (4) A. sp. These were allied to A. Hdwarsi, a small species, three with eggs and one male, always in September. (5) Polynoé sp. juv. Once in December and once in the end of March. (6) Spionid larva, occasionally from November to March. Rarely in May and July. (7) Magelona sp. larva. Fairly common in July and August. 8) Pecilochetus serpens Allen, larva. Occurred in small numbers } every month except December and April. Commonest in May and August. (9) Crrratulus sp. juv. Once only early m March. (10) Terebellid larva. Present every month, but not usually in large numbers except once in November, then rare till the end of February, when it increases and is very common in May. The houses of the very young larve are extremely pretty, the animal using all sorts of small organisms to cover itself, especially 164 MARIE V. LEBOUR. diatoms, but sometimes the case is entirely of sponge spicules. As the worm grows the house becomes transparent and hyaline. (11) Pectinaria sp. larva. Only found rarely in October and December. (12) Annelid larvee indet. Occurred occasionally but particularly from January to the end of March when they were at times abundant in verv young stages. (13) Tomopteris heligolandicus Greef. Begins in the middle of June and is very common in July, rare in September and October. Young forms chiefly from July to September. CHATOGNATHA. Sagitta bipunctata (Q. & G.). Present throughout the year, scarce in most of March, April, May and June. Very common most of the rest of the year. POLYZOA, Cyphonautes larva. Fairly common from September to the end of March, rare from April to August. Commonest at the end of March. PHORONOIDEA., Actinotrocha larva. Only seen in July and September, 1916. More common in 1915. ROTIFERA. Syncketa sp. Rare, September, October and March. CRUSTACEA. COPEPODA. Sars, G. Q., “ Crustacea of Norway, Copepoda.” (1) Calanus finmarchicus Gunner. Common on and off from the end of April to the begining of November, generally present in small numbers at other times. (2) Paracalanus parvus Claus. Unusually scarce this year except at certain times. Very common in May, common parts of August, September and October. Very common for part of November, then becomes rare or absent. (3) Pseudocalanus elongatus Boeck. Perhaps the commonest copepod here. Hxceedingly common all through the year except from the middle of May to the end of July, when it becemes rarer and is Sometimes absent. (4) (5) (6) (7) THE MICROPLANKTON OF PLYMOUTH SOUND. 165 Centropages typicus Kroyer. Common in September and October, 1915, scarce or absent through the winter, rather more abundant in May, becoming rare again in August. C. hamatus Lillj. Common in September and October, 1915, then absent until August, when it is very common on the 16th. Isias clavipes Boeck. Fairly common in May, rare in June. Temora longicornis Miiller. Very common all through the summer and in the middle of February, common in parts of November, but rather rare in winter. Anomalocera Patersoni Templeton. From September to the begin- ning of November ; not common. Labidocera Wollastoni Lubb. Not common, in July. Candacia armata Boeck. Rare through the winter, common in July and September. Parapontella brevicornis Lubb. Common in February and March and occasionally in May, otherwise rare; absent from October to February. Acartia clausii Giesbr. I find this species of Acartia the only one present in 1916. It is exceedingly abundant most of the vear, very common on and off from May to the beginning of January and very seldom absent altogether. Longipedia Scotti G. O. Sars. Once only in February. L. minor Scott. Once in water samples and once in the tow nets, June. Euterpina acutifrons (Dana). Rare, October to December. Idyca furcata Baird. Once only in December. Amphiascus similis Claus. Rare, September and October. Oithona similis Claus. More or less common throughout the year except from November to January. Very common in the middle of February and the middle of May. O. nana Grubb. Rare, January to May. O. plumifera Baird. Rare, from February to May, and im Sep- tember. Coryceus anglicus Lubb. Present most of the year, but rarest in the summer. Through October and November it agrees with Pseudocalanus in its abundance, but becomes scarce in December. NEW SERIES.—VOL XI. NO. 2. MAY, 1917. M 166 MARIE V. LEBOUR. (22) Thaumaleus longispinosus Brown. Once only in September, 1915, with eggs. (23) Caligus rapax M. Edw. Free in the tow nettings in September, December and March. On one occasion a female with eggs was present ; an unusual occurrence in the free state. Copepod naupli are common on and off for most of the year. At the end of January they were very abundant, also at the end of May and beginning of July. Calanus and Temora are the commonest forms identified. CIRRIPEDIA. ** Nordisches Plankton,” Vol. 11. Balanus nauplii occur in the beginning of February, are very common in the middle of February and continue till the beginning of May, when they dwindle and disappear except for a straggler or two in June. In the end of July they reappear and stay till the beginning of October. Cypris stages begin in the end of April and continue until the end of May, are rarer in June and disappear in July. A few were seen in September and February. The fact that there are two seasons for these larve (which is borne out by other Plymouth records) probably means that the July forms are a different species, as at Port Erin only the spring larvee occur. CLADOCERA. *“Nordisches Plankton,”’ Vol. 1. (1) Evadne Nordmanni Lovén. Begins in the end of April and grows | very common in May, is common through the summer until the middle of September when it disappears. (2) Podon intermedius Lill]. Very similar in occurrence to Evadne, but is more frequent in August and September. AMPHIPODA. Sars, G. O., “ Crustacea of Norway, Amphipoda.” (1) Apherusa bispinosa (Bate). Occurred once in October and once in January. (2) A. Clevii Sars. A few specimens once in August and twice in June. (3) Caprella sp. Once at the end of August. Amphipoda indet. Rarely in April and September. THE MICROPLANKTON OF PLYMOUTH SOUND. 167 TSOPODA. ** Nordisches Plankton,” Vol. 14. (1) Idotea viridis (Slabber). Ra1e in November and March. (2) Gnathia mazillaris (Mont.). Young larva, free, rare, December. Praniza larva once in the middle of May. (3) Microniscus sp. On Copepeds, chiefly Calanus, Acartia and Pseudo- calanus, from September to December, rare in March, most frequent in September. (4) Bopyrina sp. Rare, January and February. CUMACEA. Sars, G. O., “‘ Crustacea of Norway, Cumacea.”’ (1) Pseudocuma cercaria (P. G. van Ben). Very rare, September and February. SCHIZOPODA. ‘* Nordisches Plankton.”’ Vol. 12. (1) Nyctiphanes Couchi T. Bell. Not common, in the beginning of May only, immature. (2) Macropsis Slabberia Van Ben. Rare, December only. Siriella Clausii G. O. Sars. Once only in October. — 5 —~ ee (4) Leptomysis mediterranea G. O. Sars. Not common, November to January. Kuphausicde larve. Not common, October, November, March to May and August. STOMATOPODA. Squilla Desmaresti Risso, larva. Once only in October, 1915. MacrurRa. These are all larval forms; starting with Carcinus me@nas early in January they gradually increase and are very common through the spring and early summer, and although plentiful through August and September, fall off considerably in October, being only represented by stray stragglers through the winter. (1) Leander sp. larva. On and off from May to November. Single specimens at the end of February. Commonest in Julv. 168 MARIE V. LEBOUR, (2) Galathea sp. larva (Sars, G. O., “ Bidrag til Kundskaben om Deca- podernes Forhandlingar,’ Arch. Math. Naturw., 15, 1889-90). Begins at the end of January and continues common till May, when itdwindles and disappears in September, commonest in March. (3) Hupagurus sp. larva (Sars, ibid., 1889-90). Very rare at the begin- ning of January, continues rare through March to the end of April when it is common, continues fairly common till the middle of May, rare from June to October. Older stages occasionally in the summer. (4) Huppolyte sp. larva (Sars, ““ Account of the Postembryonal Develop- ment of Hippolyte varians Leach,” Arch. Math., ete., 32, 1911). Common June to September, specially abundant in September, continues into Nevember, and was found twice in December, rare in the spring. (5) Crangon vulgaris L. larve (Sars, “ Bidrag til Kundskaben om Decapodernes Forhandlingar,” Arch. Math., etc., 14, 1890). From February to September, never very common. (6) Ageon fasciatus Risso, larva (Gurney, R., “The Metamorphoses of the Decapod Crustaceans AZgeon (Crangon) fasciatus, etc.,” P.Z.S., Vol. II, 1903). One specimen in January. On and off from May to September. (7) Ceraphilus nanus (Kyoyer), larva (Sars, abid., No. 14). Rare, September and October. Crangonidee larvee indet. Occurred occasionally from June to October. Other Macruran larve indet. chiefly allied to H7ppolyte, common in July and August. (8) Jaxea noctiana, Trachilifer larva (Bouvier, J.M.B.A., X, N.S, 19S): Occurred once on August 16th, 1916. Unusual to find it so far’ inland. BRACHYURA. (9) Porcelluna sp. zoea (Sars, ibid., 13). One specimen on March 23rd, then begins at the end of April and in June and July is very common, continues till the middle of October. (10) Eurynome aspera (Penn.) zoea (Cano, G., “ Sviluppo ce Morphologia degli Oxyrhynchi,” Mitt. Zool. Stat. Neapel, X, 1893). Rare, March and July. (11) Cancer pagurus Li. zoea (Pearson, J., ““ Memoir on Cancer the Edible Crab,” 16th Lancs Sea Fish. Lab. Rep. for 1907). From the middle of January to March, common. THE MICROPLANKTON OF PLYMOUTH SOUND. 169 (12) Portunus sp. zoea (Williamson, C. H., “‘ Report on Larval and Later Stages of Certain Decapod Crustacea,” 28th Ann. Rep. Fish. Board Scotland, 1907). Many species, begin early in March, become very common in April and continue till September, less common from October to November, after which they disappear. (13) Carcinus maenas Leach zoea (Williamson, C. H., “ On the Larval and Early Young Stages and Rate of Growth of the Shore Crab ” (Carcinus moenas Leach) 21st Ann. Rep. of Fish. Board for Scotland, 1903). The first of the Brachyura larve to appear, arrives early in January, is specially abundant in February and continues till May, after that very scarce. (14) Corystes cassivelaunus (Penn.) zoea (Gurney, R., “The Metamor- phosis of Corystes cassivelaunus (Penn.),” Q.J.M.S., 1903). From the middle of February to July, fairly common, rare in September. Brachyura zoea indet. With a long spine like Corystes fairly common in September. Megalopa indet. Scarce, from May to November. PYCNOGONIDA. - Norman, A. M., “ The Podosomata (= Pycnogonida) of the Temperate, Atlantic and Arctic Oceans,” J. of the Linn. Soc. Zool., Vol. XXX. (1) Anaphia petiolata (Kroyer) juv. In June, September and October free, with the hind legs not fully developed. In the larval stage living in medusz common from July to September. (2) Pallene brevirostris Johnston. Occurred once at the end of October. Mo.Liusca. Polycera quadrilineata (Miill.). Once only in September, 1915. Larval Gasteropoda. On and off nearly all the year, commonest in July. Rare in mid-winter. Larval Lamellibranchiata. On and off, not very common for most of the year. Commonest in September, rare in winter. LTimacina balea Miller retroversa (Flemm.). Common in the middle of September, 1915. Occurred occasionally from July to October. Com- mon once in August, 1916. 170 MARIE V. LEBOUR. ECHINODERMATA. Holothurian juvy. Rare in December and January. Ophiopluteus. Begins in March, very common towards the end of the month, dwindles in April and disappears in May. Occurs again in August and September, common in September. Echinopluteus. A few occurred once in the middle of November, 1915, begins in May, not common. Very common at intervals in July and August. Auricularia. Rare, January and February. Very young Echinoderm larvee in March. TUNICATA. Orkopleura dioica Fol. Common from February to May and from August to September, otherwise not very common and occurring at intervals. Commonest in early April and early August. Appendicularian indet. Rare in August till November, and in February. Fish eggs and young fish were occasionally present. A Survey of the Plankton in each month both from water samples and tow nets. 1915. September (21st to 30th). Winds mainly 8. and 8.E. Weather fairly fine. Shows both groups of diatoms. Coscinodiscus species, Biddulphia mobiliensis and regia beginning, Rhizosolenia which is almost at the end of its season not common except R. Stolterfothii, which is still abundant. Skeletonema, Chetoceras constrictum and Asterionella common, Paralia fairly common. Very few Peridiniales except Prorocentrum micans which is near its maximum and Ceratium fusus. Of the other unicellular groups Laboea species occur in small numbers, Tintinnopsis ventricosa is abundant and Pontosphera Hualeyi occurs singly several times. Of the Coelenterates Phialidium hemisphericum and Obelia meduse with young Pleurobrachia are common, but no other species. Amongst the Annelids Autolytus longiferiens and rubropunctatus occur singly with eggs and a few larvee of various kinds are present. Sagiita is very common, Cyphonautes present but not abundant. Many copepods occur, Acartia, Calanus and Pseudccalanus are the commonest, also common are Centropages typicus and hamatus and Temora and Coryceus is common at the end of the month. Brachyura zoee and the larva of Hippolyte are common, Porcellana zoex and Podon intermedius are common in the middle of the month and dwindle or THE MICROPLANKTON OF PLYMOUTH SOUND. Ay (al! disappear at the end. Limacina balea tf. retroversa was common once in the middle of the month. Chief forms---Asterionella japonica, Chetoceras constrictum, Rhizo- solenia Stolterfothii, Skeletonema costatum, Prorocentrum micans, Phia- lidium hemisphericum, Obelia sp., Sagitta bipunctata, Calanus finmarchicus, Pseudocalanus elongatus, Acartia Clausii, Centropages typicus, Brachyura zoeee and Hippolyte larve. October. S.E. winds prevalent. Chiefly fine weather. Asterionella common until the middle, then dwindles and disappears. Biddulphia species not yet common. Chetoceras species common at the beginning and fall off in numbers towards the end, Lithodesmium undulatum common until the middle, Mastigloia sp. very abundant from the middle to the end of the month. Nitzschia closterium common. Paralia on the increase. Rhizosolenia Stolterfothi common at the begining but absent at the end, Shkeletonema common and Streptotheca thamensis present with it nearly all the month. Of the Peridiniales Ceratiwm bucephalum is fairly common, C. fusus present in small numbers, Prorocentrum micans continually present, Peridinium divergens sometimes fairly common. Laboea species still present in small numbers, and Tintinnopsis ventricosa, Pontosphera more frequent, very common at the end of the month. Of the Coelenterates Stomotoca dinema and Turris pileata occur although only Phialidium hemisphericum and Turris pileata are common. Besides Pleurobrachia which is sometimes common, Beroée and Bolina both eceur. Annelid larvee rare. Sagitta very common, Cyphonautes continues but 1s rare. Of the copepods Calanus is still common, but Pseudocalanus, Temora and Acartia are the commonest ; Coryceus is also very common and seems to follow Pseudocalanus closely in numbers, Centropages typicus and hamatus fall oft in numbers. All the larval Crustacea are much less numerous. Chief forms---Asterionella japonica, Chetoceras constrictum, convolutum and densum at the beginning, Mastigloia sp. from the middle of the month, Nitzschia closterium, Skeletonema costatum, Ceratium bucephalum, Prorocentrum nvicans, Phialidium hemisphericum, Obelia sp., Sagita bipunctata, Calanus finmarchicus, Temora longicornis, Pseudocalanus elongatus, Coryceus anglicus and Acartia Clausii. 172 MARIE V, LEBOUR. November. N.E. winds prevalent. Mostly cold. Asterionella much reduced in numbers. Biddulphia mobiliensis and regia both come on and are very common from the middle to the end of the month. Chetoceras species greatly reduced, almost disappearing. Guinardia common towards the end of the month, also Hyalodiscus stelliger, Mastigloia sp. in large numbers at the beginning, absent after the 8th. Paralia becomes abundant, Skeletonema very common with Streptotheca common also. Ceratiwm bucephalum and Prorocentrum micans much scarcer, the latter absent altogether at the end of the month. Tintinnopsis beroidea very common at times through the month. Hardly any ccelenterates except Phialidium and Obelia, and these disappear at the end of the month. Autolytus pictus and rubropunctatus appear with eggs. Sagitta very common, copepods abundant, Calanus becoming scarce, Centropages almost absent, Paracalanus common, Wl © Olece Ofice O2ce Zee Zeo Loe Bee co O5ee 2 © Odeo + O07ce 2ce co OF c OF7ce OF + Aco Loo OF + rr re ir r rT Od . + r + + r + co OL © 0-24 + 02 r + r + th ce +r oc co co c + iy + Ol} OZ r r ‘sinensis Grev. . . c r 1 r 0-2 r 02 r ° + O38 +r O2r Ola Io Ob r O5+ O2 co OF r Olre mr r rn favus (Ebr) vy. Heurck 4 r rr ui.) ¥. Heurek 5 O8 & r r r r ir ta) + . : r ¢ tum Ebr. . F 08+ 34 5c + OF © re OL 03 02 O68 06 hy 02 rr 05 02 05 r OT+ OF+ OF0a Boo doc Sco 05 (West) Gran oo Bice + er O2+ + rr O7 + OBce ir r 02 OL ir O8rr = + re 02 o2 OF r co O28 r O84 Vee 1+ os Q z - r r 2 iis wr rr 2 tr rr mr Mv idewGrn «2 At Br or br O65 O08 Lrg @r 5r fr Gr 2ros 06 4r 4 Ge om 84 mr le Lo Lr Lr 4+ Oo 44+ 4+ Rory (Kr 05 02 t 9p r O34 O%rr 4 ArDyp aan. FoF = = = Fo By deo Ol+ Br rir + ar t 3m rr re r r wr Or Or Sr 2 1+ roo 1650 1111 r 1880 c 12080e O43co 43% B+ Bee T+ + 6 tayGron 02 ge 02 oO ro 02 oz 05 08 08 o1 ot 05 Ol 02 03 08 re 08 Me ee ; f ; as bP if tt Boe vow Sl 14 oh : iG + BY ne GO. & ott tol MA Jt phe & Ge BOE 95 Ode 99% CEI Jats oe Oe "ae $0. yy! has i Be foo , © we [0 SO. 1S r.V-0 1 BO G0 ) yf Pr Pala, : Ty. Soa ov £0 6 T £0 9 . ad | a ee wh ea 4 1 Gt york y 8G f WG-0 a1 So . r & bO ot [0 OD « , [ > i = Ne { ee Sara Eh An ot ' ab ; a) { [4 i 0), 9b 4 -b- & ah ao a3 ( birt fh niquiaier . Avo . AuodaO guedioroohnesg es 5 tala ; od agony ica # Tal, ay batter a navel ry Pw FAs iy ag hensins 4 ; oe vials Biggi t stated eens widaitel stale i — titea’) cover ddqor \ evel) op i «dee Sct udulowtod xe t, evel) mioinsh — . pliv& eleatod 3 ral J ansiqinab 4 , ; .) 9wolOr goted .- dtide@ audiwatids A ces ybib » . SET i) edtirtoted BSD iJ . Uke Bol TiWe py fiitoe nubeikiowl | Hilde orate (reth) piohely 9” avo) oridesiviiy yall} obtelaly © y Ap 4° 2 Seed a BIB MON » edind® aiarronsedd a gig... fags & (jist) aianailidone ja astuot TA sino 2 Aosta. euvah worth) ‘ai dood se (lt) ¢ (lige) aeuserxotle ry: £; widapsts,)-e allane sinaorl Brats aaptals hoc u itisigeadb orl dink nr) (de9W" ) ith llowitdgingh mani ; ae iy ariel GidoestiA, xeitioias wolll pono si slanoitas es {soled }an (ou) (stu@ly iwradayl wrodid oft cy 40 iiqod see Sh \ (TER SF LG may eye rh ra TE) 8 Bac We TABLE I—continued. i > The Microplankton of Plymouth Sownl from the region beyond the Breakwater, showing the average number of individuals in 50 cc. for each week, also relative abundance vm the tow-nettings. The numbers show the individuals in the wnter samples, the letters their relative abuulance in the tow-nettings. 1015. Serremonn. Ocronrr. Novempen. Decemuxn, 1916. Jaxvany, Peunvary. Manon. Avr. May. Jus. Juby. Avoust. Skrre mune. Weakening . . . 25 2 9 16 23 30 6 13 20 27 4 i 18 25 1 8 15 22) 20 5 2 ty 26 4 in 18 25 1 8 15 22 29 6 13 20 27 $ 10 17 wu 1 8 15 22 29 5 2 rt) 26 2 9 “Ir A 8 a ° . r 0-2 r 1 62, Navioula ae : : OLS O3ri2e 3+ 5 Wt B+ Lr 2r 2 05 2 OlLr 4 r Wee 2 2+ r O08 + + 63. 3 Ce er ie le 4 ine freee 26 fr ar 2 2705503 O38 r 1 1 1 1 105 2 3 r rr rr r 2 1 2 4 OF 2 05 07 1 08 OF 09 5 1 1 2° OF 6 64, Biase sp. - a . . + Dy lr03r 2r 2 Qrr Birr v1 iro rt bir 8 r 2° (08 3 3 Sr 4 2 05 3 % 2 O8ir 2 O7 r 2 2r 25 rr 2m re 05 lr Oter 03 O05 O2r Lr O08 r OF F O2rr mr O83 2 1 65, Mastigloin sp. - rey aa 10 2003 rr 348105070 tr 07 1360 «12786 TL «173 ~=—«150 2 87238 4 66, Amphiprora maxima Greg.” s, . O01 OL O-L rr r mw O08 OL rr 02 od OL 03 Oo rr rr r o2 rr r eee Amphora ostracaria Bréb. . a . < 1. , . 3 re ir o2 mr rr OL Oe r o2 O02 Fr r tn Nitzschia Sloeteriam Ww. Sm. - . . O07 07 40 320 5 5 2 tx 1 2 1 2 05 O2 2 03 10-3 (0-3 o2 O07 O8 Os di 1 3 oer Bor 6 3 arr O07 4 03 OS O2 OT rm OF 2 3 a ar ay | «» sSermta Cleve . ‘ Ole 02 1 03 O05 O2rr O2 02 O8r 2 O2 4 4 6 Aer OF i v delicatissima Grey, . + 5 r Tv rr 167 cc 2367cc 906ce 17M0e 28ee BWOce Ge 2 1 3 3 2 03 We 4 Mr 6 » _ panduriformis Gm. . . OL 0-2 OL 4 ie OS OL 02 ig Bacillaria paradoxa Gm. . 5 Sos Ui Oi 2+ b r r r 2r 44 roilr 4+ r Sr r7o b + r O54 i ty Se 2 2 le © 1 1 r tr 1 2+ Ae See eee and Surrirella spp. : har O2irn r rt yr 02rr 05 6 r 1 rr 02 er r r OL re 1 1 r ir mr OL rr r 02 r O2 6 o2 fi 75, Exuviella compressa (Bailey) 3 more 04) 02 0 05 76. Prorocentram micans Ebr. . : . - 64 4.706rr 6+ 4 2 2 02 03 O2 08 On rr 03 O02 02 Os Ol 0-7 03 re O2 03 03 05 1 Us 2 05 2 O8 me OS re OF Br Tr (10re Wire We IT 77. Dinophysis acuta Ebr. a = 5 rr r O2 r mr 02+ 02+ 84 O3r 78. » aouminstaCL&bL . ° Od 3 6 2 05 03 O08 1 Og O5 79. » homunculus vy. tripos Lemm. 5 rr ‘80. me ovum Schitt . : a yd 0-2 : 04 O41 O7 1 O03 rr 02 O2 05 rr Sl. ” rotundstum CL&L, . . . rol 02 oO. 02 O4 0-2 OS mr O8 02 0-2 rr 07 O2r OSrr r O06 05 82. Glenodininm bipes Pauls . ; 5 02 Ot 02 07 2 08 1 3rr 38 12 05 05 o2 O38 83. Protoceratium reticulatum Cl. & 1. : i 07 03 O05 rr o2 03 84. Goniaulax triacantha Jorg. 5 : fs 02 o2 2 O2 08 4 85. ” eset Stein. . . 0-3 o2 O03 86. ” fera AGL &L) . 5 E 0-2 O1 05 1 05 ‘87. % “EES Kofoid ; x 2 OL OL 02 05 1 Os Oo 3 o2 88 w polyedra Stein . q 4 5 rr ir 0-6 OF 03 89. Amylax lata Meunier - o1 O1 2 02 90. Dip! cual Tenticula Bergh : y 7 r r r r r r r r o2 02 03 i luls Ostf. . c 7 2 O7 1 F roon Ob re OS O3rr lr 08 Ol Os 1 2 2 oe Oz 2 O5mr 1 03 o2 5 . 03 1 O2 ovatum (Pouchot) . . Ms r OF + rr Ir + Ir r rr 02 ¢ 0dr r 02 r O2 r O2+ r 02 4 pedunculatum Schutt ir vr re OL r » pallidam Ostf. . O41 ir On 03 ee lr r w pellucidum (Bergh.) - A = r rr m OL 1+ O6+ 1 O4r 7 Olr OF + O65 lr O2m O2 o2 05 lr 07 r 08 05 ” oceanicum Vanh. . 2 2 1 re re r rr ” divergens Ebr. : F) OL rd ec rO0le + 034+ r o r mw rr r 1 o 02 O2 0-2 rr r r r r O02 © » crassipes Kofoid - : : r + ” conicum (Gran) . . OB rOlr 3 OF} rO2 wr O38 OL r O02 r rr r r 0-5 ee + r O03 © + O2r rm Sco OF rr Ol r 07 O2 4 O4 r OF © rr rr OS ¢ O2rr + 02 ‘Thorianum Pauls, . : r ir rr 104, Poridiniacess j juy. et indet. . . c = 02 2 1 4 2 O28 5 it x Wh eer 2 105, Pyrophacus horologicum Stein . 5 r 106 Oxytoxum Milneri Murr. & Whitt, A 0-2 107, Ceratium Tae v. Daday . é: 3 r ag + r r by vy 108. ” halumi (Cleve) . . t r rO-leo 08+ cOl-or+ + + r r rr 02 r 02+ r OB r 109, " tipo (0. F. Moll). ‘ re O7 iF 110, » tripos f. lineata (Ehr.) . yi < rr 05 O2 rr ML » arcticum (Ehr.) . 5 5 Pi r 0-3 03 112. macroceras (Ehr.) : 5 . 01 cad ro r va rr r ie tt re ir 0-2 113. » furca (Ehr.) . : ; 5 r nm r rr O2 14. fusus (Ehr.) 5 ° . 06 ¢ 02 ir + O07 r Od 1 * 02 OL 02 rr r r r r 03 © + O3re o r 0 03 + 08+ lao O3 fF 02m O3co 2r 1+ Bo 1 115, Amphidinium crassumLohm, . 02 03 03 02 03 116. Gymnodinium teredo Pouchet . 02 0-2 O7 re 0-6 O83 © e v 02 02 On re Od O7 rr 1 O08 117. on ee Pouchet 02 O2 118. » vindis n. . . o2 119. “ Fiombedes Robot =. Od Od Oder Ol 07 7 7 1 1 1 1 2 OF 1 03 . Ob 120, » triangularis n.sp. mew it v4 : + Se ee Ge iessiiegheamnlr cee? in. (ioutwaleoda 30 te. (OR a Vissuvany, | ae oF cs ae ‘on ae cae a 28. 9 LB at a ei eu ; ? aA aagigaol sod? maceade Lit a1 GR x wt --« i 4 hO. ; ' vol) uerchnsto vai 7 “ae Y 2 es Cte gee pee ay Me & ‘ “+ \" . * = mA tik tn 8 4 ie 1 i ots Ss 4 09, Gout. 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(ad) etesoil A soqitt a OFT ] ; (1d) ossottows a LIL VE my . VE [Q., F ; (18) seiesorem SEL {t ‘7 " P r Ar dil) souk $ #41 3 aide ! fe 5 Gr, 7 E (co) arrest EE fetal wy eaate nuinibidassé cll Ak et TO (j : 4) todsood abotat nuiothoantys) ALL toslouro ot 4 agurohweaq ms ie aie eibintr PP Obl {+} Me did 12 saksiod cnc bY tf qed aielirgnsrsd et OEE o2 q TABLE I—continued. The Microplankton of Plymouth Sound from the region beyond the Breakwater, showing the average number of individuals in 50 ce, for each week, also relative abundance in the tow-nettings. The numbers show the individuals in the water samples, the letters their relative abundance in the tow-netlings. re G 4 = 15. Serremuer, — OcTouen, Novyearexn. Decemprn, 1916, Jaxvany. Frunvany. Mancu. Avni May. JUNE. ‘ Juty. 7 Weck en ener Mate omnes OUNCE IING 2s) Coss 22 20 Sez Me) ae Ie ZS a2) St a ek so a OO OG ag Se um minor, ap ° . . . 7 O56 O2 o2 ium im ander. . . 2 . is Sgt seo Peet ee Or 02 2 rr 0 o1 r O41 1 O6n 04 08 2 4 O8 OB mua he oe ba ae ee i i crassum Pouchet . : . Og 02 125. », glaucumnisp, o2 OOr O1 2 al 1 1 08 05 07 © (07 2 07 OF 1 2 196, Cochlodiniam hlix (Fonabet) » = ’ pa p pee ee . : & F i Pouchetia armata Dogiel = c o2 A ’ . Mine ys 02 02 02 10. : ssohate Beg es \ ‘s : 3 on 131 jirikos Schwaraii Bits < . 2 +h ae ares Wericohnat : c 02 O08 O5 1 1 OG 1 9 5 1 1 Og t r 02 O38 O07 re OE 3 133 Byroayatis Junula Schitt - > 5 ce a O38 re 02 2rr 02 134. Oxyrrhis marina Duj. . ’ : " Pa Plagillater. 135, Phwocyatix Pouchotii (Hériot) 5 7 " 19 70 12 8 4 ll 02 1 136. Dinobryon sp. . : < 5 A 3 07 137. Carteria sp. . ‘ : . 03 03 1 138. ‘Trochiscin | Clevei Lemm. : : : OL On 139, Halosphwra viridis Schmitz : : . Ol O02 OF On On O08 o2 oz o2 05 o2 o2 oz ay taindet. =. 2 OL 5 5 Oy O1 O41 03 Og 1 07 07 1 08 O06 ie ips aanes Houxleyi Lohm, . * 02 02 03 i ‘142. Dictyocha fibula Ehr- . . . 02 O2 O1 O03 02 Ol O2 0-2 o2 OL Ol OL Od 2 Os O2 05 1 “ Nagi Dieiptancsspemian(Eir}) : . 101 o2 o8 1 - 03 04 08 02 1 02 02 06 02 O02 OF 1 07 i. ees 144. Amoba oS re 02 02 03 02 1 4 05 02 1 07 03 a2 og On M6. eines 8 Clk rOl rO2rO2c OF 1 OS rOlrO®r + 02 rO2re OH+ OB r04+ 03 03 Le Wo R07 Veyse wee Oboe 02 r 02 02 - net , 146, Heliozoa indet. . . , Ir - ~ Ae ‘147, Acanthochiasma fusiforme Hucokol —. 2 O01 or Oo O03 2 1 OF mr + Ir rr 02 O2r v2 Oe nr Os 148. Lithomelissa sotowa Jérg. . . “ . cd rr re tr tr . 149, Amphimelissa sotoas Cleve . . : . 02 OL r OL : 150. Paracineta limbata Maup. ? On 151, Avineta tubcrosa Ehr. v. Fraiponit Fr. | ° rr O2 ie Lachry? 02 MOAT SP. . ‘ ‘ “ . (bY 153. Coleps s) : . : ¥, O1 O2r r od 154. Tiarina fususCL&L =. st 02 02 On Sir 07+ O8 O38 1 ) 165, Mesodinium sp. 5 a) . 5 ‘i O1 02 0-2 0-3 O-7 0-3 2 OF OL 1 1 O41 0-2 o2 02 Og o2 1 1 156, Nassula sp. Serer fe 02 02 02 065 03 167! Btedmibidiom otudatum From, “i o4 02 aa 168. Laboea conica Lohm. ‘ 08 Ot OL 02 O1 1 02 O05 Od 02 03 05 O1 0-3 O02 1 1 Og 0-2 OS OF O05 oo 03 0-5 159. =, strobila bohm. =... Od OD O41 : 03 TEM DERE On acuminata Ceawe é 5 01 OL 02 OL 2 2 2 Od 0-3 iralis Leegaard : : on OL O2 O41 1 OR o2 Ol nora 1 2 04 05 08 O02 O68 05 03 03 O3rr 02 O2 02 O2 O02 Lr O47 Ol Fr 07 05 r 07 OF O28 OF OFF 03 07 : ; 163. Lolinantolls oviformis Leogaard . 5 P og ] hn Euplotes vannus O.F M . ° : O41 =p. » 0-2 05 02 the ‘Tintinnus subulatus Ebr. 4 " 01 r 02 rr rr ; OB 1 O07 O08 lier lr ole 08 07 03 ce Tintinnopsis beroides (Stein). : . 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OS 7 é 3S oS Je. 2) en gE ef rm - Gl 4 , ay aé eo : DEF AN: < aan oa ae SET MM {2 ; AG - ize { Ob-f 1G 2a bff ag : & i Fy i ey-L GB 407 oe 3 , ee & ie a oI Ea hy fei F x 8 vidlaes9e ra Fe f ee an 28 cy a : - e ¥ oF Bb-f 22 T ao ~ a i Oi-§ 601 0a ul Wr ‘ f a, acy 00. iy SG + nc QS ‘ d I 4 ob-Y as gc ai Mee ee ee #ae et . T Tei is : sass - TL ytd ii bat fey root te een [ 183 ] The Peridiniales of Plymouth Sound from the Region beyond the Breakwater. By Marie V. Lebour, M.Sc., Assistant Lecturer in Zoology, Leeds University. Temporary Naturalist at the Plymouth Laboratory. With Figures 1-14 in the text. THE following list includes all the Peridiniales identified in the plankton throughout the year from September, 1915, to September, 1916, from the water samples, details of which will be found in another paper in the same journal (p. 133). Also from the plankton in the tow nets in the same year and a portion of the summer 1915. As is shown in the above- mentioned paper, the summer is the time for nearly all the Peridiniales, June being the maximum month. After October very few are seen in the water samples, although in the tow nettings the larger and stronger forms, such as Ceratiwm and Peridinium, are still present. The new and least-known forms belong to the Gymnodiniacee, which have no cellulose sheath. Perfectly transparent and extremely thin cases, however, are often seen which may be close fitting or many times larger than the gymnodinian. Pouchetia and various species of Cochlo- dinium are instances of this (see Plate IT, Fig. 14). The Gymnodiniacee are perhaps the most interesting of the Peridiniales, as many of them obtain nourishment holozoically and often the food can be determined. Throughout June the flagellate Phaocystis pouchetii was excessively abundant, and this furnished food for many gymnodinians (e.g. Gymmno- dinvum rhomboides and G. triangularis, see Plate I, Figs. 6 and 7). Division stages in this group are often seen which in the genera Gymno- dinium and Spirodinium take place usually, if not always, in the free state and not in capsules as in Pouchetia and others (Pouchet, 1885 ; Dogiel, 1906). Although no special investigation has been made closer inshore, the examination of a few samples of water show that many of the species occur near the land, such as Gymnodinium and Spurodinvum species and Dinophysis, besides several species of Peridinium. 184 MARIE V. LEBOUR. In the following list 60 species are recorded. Of these 5 of Gymno- dinium, 2 of Sprrodinium, and one of Cochlodinium are new. Twenty-one species are, I believe, new records for British seas and 28 are new records for the Plymouth area. In addition to those recorded and described there are many which I have not been able to identify. Some of these are young forms, others collapsed before they could be properly observed, and others were distorted. Among these there are probably many new species belonging to the Gymnodiniacee. The classification adopted is that of Paulsen (1908) in ‘“ Nordisches Plankton.” Those marked * are new to Plymouth, those marked N.R. are new records for British seas. PROROCENTRACE. Genus EXuUVIELLA Cienk. (1) * Exuviella compressa (Bailey) Ostenfeld. Occasionally in water samples in the summer. Genus PRoRocENTRUM Khrenberg. (2) Prorocentrum nucans Khrenberg. From May to October in the water samples, rarely in tow nettings. Commonest in the late summer. Its maximum early in September. PERIDINIACE. Genus Drnopnysis Ehrenberg. (3) Dinophysis acuta Khrenberg. Fairly frequent in very fine tow nettings, not so common in the water samples. May to October. (4) D. acuminata Cl. and L. Common in water samples, usually gets through the very fine net. There is a small form of this species which occurs more rarely than the type in the spring and early summer. (5) D. ovum Schiitt. Occasionally in water samples. (6) D. rotundatum Cl. and L. Common in water samples. (7) D. homunculus Stem v. tripos Gourr. Occurred once only in tow nettings, August, 1916. Genus GLENODINIUM (Ehrenberg) Stein. (8) * Glenodinium bipes Pauls. Common from May to September. Abundant in May and June with its maximum in early June. This species is so small that it always gets through the very fine THE PERIDINIALES OF PLYMOUTH SOUND. 185 net. It is exceedingly active and lives many hours in a bottle of sea-water. Genus ProroceRAtTiuM Bergh. (9) * Protoceratium reticulatum (Cl. and L.). Occurs fairly commonly in water samples from May to September, commonest in August. Genus GONIAULAX Diesing. (10) * Goniaulax triacantha Jorgensen. Rare, in water samples, May to September. (11) G. polygramma Stein. Rare, in water samples, May to Sep- tember. (12) G. spinifera (Cl. and L.). This is the commonest species of Goniaulaz. May to September. (13) N.R. G. scrippse Kofoid. Occasionally in the water samples, July to September. (14) G. polyedra Stein. Occasionally in water samples, May to Sep- tember. Genus AMyLAx Meunier. (15) N.R. Amylax lata Meunier. Occurred a few times singly. Slightly smaller than the type. Genus DipLopsauis Bergh. (16) Diplopsalis lenticula Bergh. Fairly common in very fine tow nettings and in water samples. May to September. (17) N.R. D. pillula Ostf. This minute species is abundant in June in the water samples, very often with Glenodinium bipes. Genus PERIDINIUM Ehrenberg. Sub-genus PROTOPERIDINIUM Bergh. (18) Peridinium orbiculare Paulsen. Occurs rarely in the water samples. (19) * P. cerasus Paulsen. This little species is one of the commonest and easily recognised. Occurs fairly frequently but never in large quantities in the water samples. (20, * P. roseum Paulsen. Very like the last species but larger and flatter. Occurs rarely in the water samples. 186 MARIE V. LEBOUR. (21) P. ovatum (Pouchet). Common in late summer but rare in May and June. Specimens with broad and conspicuously striated interspaces between the plates are as common as the typical forms and are probably older, as Mangin (1913) has already noted. More common in tow nettings than in water samples. (22) P. pedunculatum Schiitt. Very rare, in water samples only. (23) P. pallidum Ostf. This and the following species are both common, the present species being larger is commoner in the tow nettings. (24) P. pellucidum (Bergh). Common in water samples. Sub-genus EUPERIDINIUM Gran. (25) P. oceanicum Vanh. Rare in tow nettings. (26) P. divergens Ehrl. Abundant in the tow nettings, especially in August and early September. Following Meunier (1910) I have reunited the P. depresswin of the ‘“ Nordisches Plankton” with this species. (27) P. crassipes Kofoid. Not very common in the tow nettings in August and September. (28) P. conicum (Gran). This species and P. divergens are almost the only peridinians to be found in winter: although not abundant P. conicum is found throughout the year both in tow nettings and water samples. Commonest in early spring. (29) N.R. P. Thorianum Paulsen. Rare in water samples in June. Meunier (1910) gives good figures of this species, which resemble the Plymouth form more than do Paulsen’s. The present speci- mens have small knobs conspicuously ornamenting the skeleton which are very characteristic. Genus PYROPHACUS. (30) N.R. Pyrophacus horologicum Stein. Occurred very rarely in tow nettings in August. Genus OxytToxum Stein. (31) N.R. Oxytoxum Milnert Murr. and Whitt. I have referred to this species, a very small Oxytoxum about half the size of the type but agreeing with it in form. Only one specimen was found in August in the water samples. THE PERIDINIALES OF PLYMOUTH SOUND. 187 Genus CERATIUM Schrank. (32) N.R. Ceratium platycorne V. Duday. Rare, occurred singly two or three times in the tow nettings. (33) C. bucephalum (Cleve). Occurred sparingly in tow nettings in early summer, more frequently in the late summer months. (34) C. tripos (O. F. Miill.). Occasionally in water samples and tow nettings. A variety which approaches the form lineata (EKhrb.) and which I have referred to this variety occurs more frequently (Fig. 1). This has a short and straight apical horn, the hind horn nearly straight and the right horn about one-third as long as the left. The usual markings are longitudinal striations from the apex to the girdle, sometimes also with reticulations. Fig. 1.—Ceratium tripos (O. F. Mill.) £. lineata (Ehrb.). x 466. Although apparently nearest to the form lineata, the apical horn is very much shorter—less than half the length from its apex to the girdle. (35) * C. arcticum (Ehrb.). Very rare, in tow nettings, 1915. (36) C. macroceras (Ehrb.) Cleve. Rare in tow nettings. (37) C. furca (Bhrb.). Occasionally, in tow nettings and water samples in summer. (38) C. fusus (Khrb.). The commonest Ceratiwm here. Occurs both in tow nettings and water samples and is often the only peridinian present in the winter. Maximum in October. GYMNODINIACE. By far the greater portion of the Peridiniales of this area belong to this group and are missed almost entirely by the tow nets, only a few of the larger forms being retained by them. 188 MARIE V. LEBOUR. Genus AMPHIDINIUM Cl. and L. (59) N.R. Amphidinium crassum Lohmann. I have referred to this species, a form between A. crassum and A. longum of Lohmann, but which is slightly larger than either of these (Fig. 2). The shape of the body is not so pointed posteriorly as in A. longum but not so broadly rounded as in 4. crassum, the greatest breadth being in about the centre of the body. The nucleus is posterior as in both forms, and a coloured body, greenish, is situated just in front of the nucleus and behind the transverse groove, with small refractive bodies scattered round it. This is perhaps the remains of ingested food material. A thin transparent covering can sometimes be seen detaching itself from the body. Length Fig. 2.—Amphidinium crassum Lohmann. x 466. N=nucleus. of body 0-030 mm. The only record so far of this species is by Lohmann from Kiel. Genus GYMNODINIUM Stein. (40) LR. Gymnodinium teredo Pouchet. Fairly common in July and August in the water samples in 1915, less common in 1916. This is the only gymnodinian found here in the winter months, but then only rarely. It turns up singly nearly all the year round. Many abnormalities and deformities occur and a variety of shapes is seen. (41) N.R. G. pseudonoctiluca Pouchet (Fig. 3). To this species I refer one which agrees well with one condition of the above species, but which I never saw with the long contractile tentacle described by Pouchet (1885). It only occurred twice, the first time in medium tow nettings in July, 1915, and the second time in the water samples in June, 1916. It is rather smaller than the type (length 0-10 mm.). The ventral surface on each side of the longitudinal groove is pulled out into a flap, the left flap shghtly longer than the right. The bright yellow chromatophores radiate from the centre. The longitudinal groove is more marked than in Pouchet’s figures. The nucleus is in the centre of the body. THE PERIDINIALES OF PLYMOUTH SOUND. 1&9 (42) G. viridis n. sp. (Fig. 4). Closely related to the last species is one also found only singly and which is less than half the size. In shape it is much like G. pseudonoctiluca with a cap-like anterior Fia. 3.—Gymnodinium pseudonoctiluca Pouchet. 466. a side view, b ventral view. N=nucleus. C=chromatophores. OPMec0csvYZ S Ez Se, Fic. 4.—Gymnodinium viridis n. sp. x 466 a side view, b ventral view. C=chromatophores. end; the longitudinal groove, however, reaches back slightly o ver the dorsal surface posteriorly so that the hind end is divided. The chromatophores are of a greenish yellow colour, not bright yellow as in P. pseudonoctiluca. Length 0.06 mm. Occurred once in June. 190 MARIE V. LEBOUR. (43) G. achromaticum n. sp. (Fig. 5). Related to G. viridis but without chromatophores. Perfectly colourless and trans- parent, transverse groove conspicuously left-handed, longitudinal groove reaching to the extreme posterior end. Apex somewhat excentric. Body covered with longitudinal striz. Nucleus posterior. One specimen only in July, 1915. (44) N.R. G. rhomboides Schiitt (Fig. 6). One of the commonest in this area appears to be the species figured by Schiitt (1895, Plate X XI, Figs. 63, 1 and 2) with the above name. Apparently no description of it exists except the short diagnosis in “ Nor- disches Plankton” (p. 99). Certain aspects of my specimens agree very closely with Schiitt’s figures, and I have therefore taken the name given by him rather than create a new one. Fic. 5.—Gymnodinium achromaticum n. sp. 466. a ventral view, b side view. N=nucleus. The species referred to by Dogiel (1906) as Gymnodinium spirale v. obtusum is from his figures certainly a true Gymnodinium and not a Spirodinium, to which now G. spirale and all its varieties have been transferred. The original figures by Bergh of G. spirale show it to be a Spirodinium with the ends of the transverse groove far apart, moreover Schiitt’s figure of v. obtusum shows also the same character. Dogiel’s species probably belongs to G. rhomboides or else some closely related form. His specimens, however, are very much larger than mine. His figures of the stages in division show it in another form which is also common with us and which I have found in division and very similar to Dogiel’s figures. Schiitt’s figure 63, 1 is also of this type, and apparently this is the form before and during division. These two forms I have therefore placed together as Gymnodinium rhomboides. The body is elongated, oval or rhomboidal, the transverse groove is only slightly displaced and_ left-handed, THE PERIDINIALES OF PLYMOUTH SOUND. 191 the longitudinal groove is inconspicuous. The whole surface is covered with longitudinal striz, those on the anterior portion being further apart than those posteriorly. Remains of food in b- ans.) rare er ae Oa Gy) Z| x4 Z) ni Fie. 6.—Gymnodinium rhomboides Schiitt. x 466 a side view, ) dorsal view, c ventral and dorsal views of older forms containing food masses of Pheocystis, d@ young form containing a Thalassiosira, e division. N=nucleus. F=food. a ball is often seen in the hind portion of the body. Nucleus anterior. The body colourless with no chromatophores. Its food consists very often of Pheocystis pouchetii when that flagellate is abundant, at other times of diatoms ; remains of Thalassiosira and Coscinodiscus were also found inside the body. Division takes place in the free state as described and figured by Dogiel. 192 MARIE V. LEBOUR. This is perhaps the commonest gymnodinian and occurs close to the shore as well as beyond the Breakwater. Length of body 0-040 mm. to 0-050 mm Fic. 7.—Gymnodinium triangularis n. sp. 466, a ventral view showing contained Pheocystis, b side view. F=food. (45) Gymnodinium triangularis n. sp. (Fig. 7). Closely related to G. rhomboides, but triangular in outline (the base of the triangle posterior) and without longitudinal striz on the body. Rare in water samples in May. This species had also been feeding on Pheeocystis pouchetii, remains of which were recognisable inside it. Length 0.045 mm. Fie. 8.—Gym .odinium minor n. sp. < 466. a dorsal view. 6 ventral view. N—=nucleus. (46) Gymnodinium minor un. sp. (Fig. 8). This little species is transparent and destitute of any sculpture. It is nearly spherical but with the posterior end slightly narrower than the anterior. Transverse groove left-handed and only slightly displaced, longi- tudinal groove reaching to the posterior end. Nucleus nearly THE PERIDINIALES OF PLYMOUTH SOUND. 193 central; green masses, probably food material, at the anterior end. Length 0-028 mm. Occasionally in water samples May to July. (47) Gymnodinium filum n. sp. (Fig. 9). Body long and narrow, tapering to a thread-like point posteriorly. Anterior end conical. Transverse groove almost straight, longitudinal groove reaching about three-quarters of the way to the posterior end. Nucleus behind the centre. A dark brown mass (probably food remains) in front of and at the side of the nucleus. One specimen was found with no coloured body. Body clear and colourless with no striz. Length 0-065 mm. Rare in water samples July, 1915. Very fragile and easily collapses. Fic. 9.—Gymrodinium filumn. sp. x 466 a side view, b ventral view. Genus SPIRODINIUM Schiitt. (48) N.R. Spirodinium fisswm (Levander) Lemmermann. Occurs occa- sionally in August and September in water samples. Conspicuous from its yellow colour and peculiar dorso-ventral flattening. Division in the free state was noticed in September. (49) N.R. Spirodinium spirale (Bergh) (Fig. 10). This species is exceedingly common in the water samples in many varieties. The typical form which agrees with Pouchet’s description and figure (1885, p. 67, Plate IV, Fig. 30) is usually much smaller than his specimens and generally colourless, although bright yellow examples are sometimes seen, such as Pouchet himself observed occasionally. The yellow examples are always blunter at the apex than the type which is pronouncedly acuminate. My specimens, including the yellow forms, measure generally 0-04 mm. to 0-06 mm., whereas Pouchet (1883-85) gives 0-10 mm. as the typical size. The longitudinal striations are characteristic, 194 MARIE V. LEBOUR, and green remains of food are sometimes to be found inside the body, also small roundish masses of fat. The variety acutum Schiitt (Plate X XI, Fig. 66) is also found, which seems to be close to the typical form and more nearly the size of Bergh’s (1882) and Pouchet’s specimens. Length of this variety 0-14 mm. One specimen which occurred in August, 1915, was coloured a beautiful carmine, the colour running along Fic. 19.—Spirodinium spirale (Bergh). *« 466. a typical form, 6 and c v. obtusum Schutt, d v. acutwm Schiitt. the lines of the strize in droplets. Other specimens are quite colour- less. The variety obtusum Schiitt is also common but of small size. Length 0-06 mm. usually. Characterised by its blunt apex. (50) Spirodinium concentricum n. sp. (Fig. 11). This species is characterised by the sculpture of concentric strive on the body, the longitudinal strize beimg arranged concentrically round a certain point at the side or on the dorsal surface. Body colourless. Grooves and shape of the body very much like the variety obtwsum of the preceding species. A large and a small form exist, the larger form being several times the size of the smaller. Both rare, only in the summer of 1915. THE PERIDINIALES OF PLYMOUTH SOUND. 195 (51) N.R. Spirodinium crassum (Pouchet) (Fig. 12). I have referred to this species a somewhat rare form which is definitely smaller than the type, length 0-075 mm. (type 0:12-0:2 mm. Fia. 11.—Spirodinium concentricum n. sp. 466. a large form, 6 small form. Pouchet). In shape and contour of the furrows it corresponds and has a diffuse colouring of brownish red beginning at the apex and following the transverse furrow. Faint longitudinal strize Fic. 12.—Spirodinium crassum (Pouchet). x 466. a ventral view, b dorsal view. are present ; transverse furrow with its ends widely separated, longitudinal furrow weakly developed. Nucleus posterior. Interior of body full of large granules. Occurs occasionally in June. 196 MARIE V. LEBOUR. (52) Spirodinium glaucum n. sp. (Fig. 13). This is a very common species, perhaps the commonest Spirodinium in this area. It begins in May, having its maximum in May and June and persists till October. A large yellow body posteriorly is characteristic, although this may be absent in young forms and Fic. 13.—Spirodinium glaucum n. sp. x 466. a ventral view, b dorsal view, c—f division stages. N—=nucleus. possibly is only food remains, although it is always the same colour and in the same place. These yellow bodies are also some- times absent in divisional stages. The body is elongated with a long anterior and short posterior portion, with a few wide apart longitudinal striz. Transverse furrow with the ends wide apart ; longitudinal furrow short and with the appearance of a THE PERIDINIALES OF PLYMOUTH SOUND. 197 three-cornered bite having been taken out of the posterior end. This species is rather like G. teredo, with the exception of the chromatophores which are numerous in the latter species. Cell colourless except for the yellow mass. Nucleus in the region of the transverse furrow. Divisional stages are often seen in the free state, one individual pushing part of its body backward so that a chain of two is formed very much like the figure given by Pouchet of the division of S. spirale (loc. cit.). Earlier stages in division show that the longitudinal flagellum persists as is described by Dogiel in his Gymnodinium spirale v. obtusum. A growth then takes place at the side of the whole body, so that the cell is very much swollen transversely ; then division takes place, begin- ning at the posterior end as a groove and half the cell is pushed backwards so that the chain of two individuals is formed, one attached to the side of the posterior end of its fellow by its extreme anterior end. After division the individuals are small and may Fia. 14.—Cochlodinium pulchellum n. sp. X 466. or may not contain yellow bodies. In one case the yellow body appeared to be dividing at the same time as the cell, which perhaps shows it to be a chromatophore. Genus CocHLODINIUM Schiitt. (53) N.R. Cochlodinium helix (Pouchet). Occurs occasionally in the water samples in August, sometimes free, sometimes enclosed in a spacious perfectly transparent covering. (54) N.R. Cochlodinium pellucidum Lohmann. Rare. In the water samples in July and August. (55) Cochlodinium pulchellum un. sp. (Fig. 14). This species was found once only in the water samples from 7 fathoms, August, 1915. It is perfectly colourless and contained in a roomy trans- NEW SERIES.—VOL. XI. NO. 2. MAY, 1917. (0) 198 MARIE V. LEBOUR. parent case in which it rotates freely on its longitudinal axis. It is fusiform in shape, and pointed in much the same way at both ends. The transverse furrow makes three complete turns and is deeply grooved. The longitudinal furrow is inconspicuous, making over one turn round the body. Nucleus nearly central. Length of body 0-05 mm., length of case 0-65 mm. This species is very similar to Pouchetia fusus Schiitt, but without the conspicuous lens and stigma of that form. Genus PoucHETIA Schiitt. (56) N.R. Pouchetia armata Dogiel (1906). This species, with its charac- teristic stinging capsules, is common in the water samples, especially in May and June. It is sometimes contained in a case, sometimes, and more usually, free. Division into two within the case was seen. So far this species has only been recorded for the Mediterranean. (57) N.R. Pouchetia parva Lohmann. This is fairly frequent in summer, especially in June. The case fits very close to the body, much closer than in P. armata. Division in the case is often seen. This species is very like Pouchet’s figure (1885) of P. polyphemus v. migra, the pigment, however, in his species is red and this is always black. (58) N.R. Pouchetia fusus Schiitt (1895). Occurs rarely in September. _ Conspicuous from its elongated body and large lens with dark red pigment. In one case the pigment mass was breaking up into small red spots. The specimens seen were always free. Genus PoLyKrikos Biitschli. (59) N.R. Polykrikos Schwarzii Biitschli. Occurs occasionally in tow nettings and water samples from May throughout the summer. PYROCYSTEZ Apstein. Genus Pyrocystis Murray. (60) Pyrocystis lunula Schiitt. Occurs occasionally in tow nettings in August and September in various stages of division in the semilunar cases. Incertae sedis. (61) N.R. Oxyrrhis marina (Duj.). The position of Oxyrrhisis stilla vexed question, and although Senn (1910) regards it as a true peridinian, the view is not universally accepted (see Klebs, 1912). In my opinion it is more of a peridinian than a true flagellate, the division THE PERIDINIALES OF PLYMOUTH SOUND. 1$9 stages of Gymnodinium and Spirodinium being closely related to those of Oxyrrhis. Oxyrrhis marina occurs sparingly in the water samples, but is to be found in great abundance in cultures in the laboratory in which it thrives with the greatest ease. In cultures of Nitzschia clostervum especially it flourishes in enormous numbers, the body being full of this diatom on which it feeds. LITERATURE. 1882. Bercu, R. 8. “ Der Organismus der Cilio-flagellaten.”” Morph. Jahrb., Bd. 7. 1906-8. Byerave, W. “ Report on the Plankton of the English Channel in 1906.” M. B. A. International Fisheries Investigations, 1906-8, Cd. 4641. 1897. Cieve, P. T. “ Plankton Researches in 1887.” Kongl. Svensk. Vetensk. Akademiens Handlingar, Bd. 32, No. 7. 1900. —— “ The Plankton of the North Sea, English Channel and the Skagerak in 1899.” Jbid., Bd. 32, No. 2. 1906. Docret, V. “ Beitrage zur Kenntnis der Peridineen.” Mitt. aus der Zool., Station Neapel, 18 Bd. 1903a. Goucu, L. “ Plankton, English Channel, February, May, August, and November, 1903 and 1904.” Bull. d. Rés. acq. pend. 1. c. périod pub. p. 1. Conseil International pour VExploration de la Mer. 5 19036. —— “ Report on the Plankton of the English Channel in 1903.” M.B.A. International Fisheries Investigations, Cd. 2670. 1905. —— Cd. 3837. 1912. Gran, H. H. “ The Plankton Production of the North European Waters in the Spring of 1912.” Bull. Planktonique, 1912. 1907-14. Herpman, W. A. and Scott, A. “ An Intensive Study of the Marine Plankton around the South End of the Isle of Man.” Parts I-VIII. Reports for 1907-14 of the Lancashire Sea Fisheries Laboratory. 1912. Kuess, G. “ Ueber Flagellaten und Algen—ihnliche Perideen.” Verhandlungen der Naturhistorisch-medizinischen Vereines zu Heidelberg, N.F. Bd. 11, July, 1912. 1908. Lonmann, H. “ Untersuchungen zur Feststellung des Vollstin- digen Gehaltes des Meeres an Plankton.” Wissenschaftliche Meeresunterserchungen h.v.d. komm. z. wiss. unters. d. deutschen Meere in Kiel, 1908. s MARIE V. LEBOUR. . Manein, L. “Sur la Flore planctonique de la rade de Saint- Vaast-la-Hougue 1908-12.”’ Nouvelles Archives der Muséum d’ Histoire naturelle, 5 Sér., 1913. . Meunter, A. “ Duc d’Orléans, Campagne Arctique de 1907.” Microplankton des Mers de Barents et de Kara. . Pauusen, O. ‘“ Nordisches Plankton,” Vol. VIII. ‘“‘ Peridiniales.” Poucuer, G. “Contribution a l’Histoire des Cilio-flagellés.” J. de Anat. et de la Phys., 1883. . —— “* Nouvelle contribution & Vhistoire des Péridiniens marins.”’ 1 SENN, G. “ Oxyrrhis, Nephroselmis und einige Huflagellaten.” Zeitsch. Wissens. Zool., Bd. 97. . Scuurt, F. ‘Die Peridinien des Plankton Expedition.” I Thiel. [ 201 ] Some Parasites of Sagitta bipunctata. By d Marie V. Lebour, M.Sc., Assistant Lecturer in Zoology, Leeds University. Temporary Naturalist at the Plymouth Laboratory. With text Figures 1-6. Sagitta has been several times noticed as a host for various parasitic worms, notably a larval nematode and several trematodes. Larval cestodes have also been seen in it. It is exceeding voracious and ap- parently eats almost any animal food, especially its own species and small crustacea, so that it is not to be wondered at if it forms a con- venient intermediate host for many worms, and as Sagitta itself is an important fish food it naturally follows that the adults of these parasitic worms are usually found in fish as their final hosts. So far, however, the hfe histories of the larval forms hitherto found have not been deter- mined, so we are pleased to be able to identify two trematodes belonging to well-known species which inhabit Sagitta as intermediate host and fish as the final host. Busch (1851) and Leuckart and Pagenstecher (1858) have described several larval trematodes and a nematode from Sagitta, Ulianin (1871) a nematode, and Pierantoni (1913) a nematode. The latter nematode is probably the same worm found in Sagitta in Plymouth Sound. Busch’s description of a nematode in Sagitta is too vague to recognise it, and unfortunately Ulanin’s paper has not been available for reference. Leuckart and Pagenstecher mention two larval trematodes from Sagitta germanica (=Sagitta bipunctata Q. and G.), one a monostome and the other a distome. Although these are figured, they are neither described nor named. The distome (Plate XXI, Fig. 9) is probably the larval Derogenes varicus which occurs in Sagitta bipunctata in Plymouth Sound. Busch’s trematode larve found in Sagitta cephaloptera (=Spadella cephaloptera) were identified by him as Distomum papillosum Diesing (=Distomum beroé Will (1844)) and two new species, one of which he names Distomum fimbriatum and the other Distomum crassicaudatum. Distomum papillorum appears to be a larval Hemdurus, D. fimbriatum 202 MARIE V. LEBOUR. is not described sufficiently to recognise, and D. crassicaudatum seems also to be a species of Hemiurus. As Derogenes is a genus closely related to Hemiurus it is interesting to find that both inhabit Sagitta as an inter- mediate host. In Plymouth Sound the only species of Sagitta is S. bipunctata Q. and G. In 1916 Mr. Smith called my attention to the number of parasitic nema- todes in it from old plankton samples. Afterwards it was found to be very common in the fresh samples and quite the commonest parasite of Sagita. It is a larval Ascaris, and in all probability is the same species as that described by Pierantoni (1913) from Sagitta in the Bay of Naples, and he has also found them from Villafranca, Wimereux and Trieste. In his brief note on the worm he suggests that it may be identical with an Agamonema described by Stossich from a Ranzana, one of the Molide. The final host of the nematode from the Plymouth Sagitta is quite un- known, but one would expect it to be something common judging from the frequency of its occurrence. This larval Ascaris occupies the body cavity of Sagitta, lying length- wise, and sometimes is three-quarters the length of its host. The figure here given (Mig. 1, Plate I) is from a small specimen. The body is colour- less and measures 3 to 17 mm. in length and is very narrow. The an- terior end is provided with a large larval hook for boring; the cesophagus is long and prolonged behind by the side of the intestine into a blind cesophageal sac: the intestine which occupies nearly the whole of the body, since the reproductive organs are not yet present, gives off for- wards a second blind sac, the blind intestine, which runs along by the side of the cesophagus. The anus is near the tail, the latter ending in a small sharp spike. The brain is plainly seen as a broad band anteriorly running round the cesophagus, and just behind it is the excretory pore from which can be traced the thin excretory duct. A large proportion of the Sagittee brought in by the tow nets is infected with this nematode. Two trematode larvee are also common in the local Sagitta, the larva of Derogenes varicus (O. F. Miiller) and the larva of Pharyngora bacillaris (Molin). Both of these inhabit common fish in their adult state. Derogenes varieus is one of the commonest trematodes with a wide distribution, and oceurs in a number of different fish. Odhner (1906) states that about a dozen and a half northern fish are recorded as its hosts. Nicoll (1914) quotes twenty-eight different fish as its hosts from the Channel, Coffus, various Gadide and a few Plemonectids are the common hosts. It occupies the stomach of these fish. Levinsen (1881) records the larval form of this trematode from Har- mothoe imbricata, and finds the remains of this annelid in the stomach of Cottus, It is very interesting to find the larva in the Sound inhabiting SOME PARASITES OF SAGITTA BIPUNCTATA. 203 Sagitta, which looks as if Derogenes varicus had a different intermediate host in the open sea than it does near the shore. The larger larvee of Derogenes varicus which are found in Sagitta have nearly all the adult characters (Plate I, Fig. 2), and the smaller ones are found in intermediate stages and are easily recognised. That we have to do with the true Derogenes varicus is placed beyond a doubt by the occurrence of a mature specimen in Sagitta which bears eggs (Plate I, Fig. 4). A parallel case is found in Echiurus pallasii (Greef, 1879) which contained a mature Distomum, D. echiuri Greef, and other cases of trematode larve producing eggs have been recorded, although they are rare. The present specimen has only a few eggs, whereas in the ordinary adult stage in a fish they are very numerous. A curious fact noticed is that all these larval Derogenes varicus are beset with small spines, whereas it is a characteristic of the adult that although it has sometimes a wrinkling of the skin it is unarmed and usually smooth. It is possible that these wrinkles may be the remains of the spines fused together. The spines are specially distinct in the younger specimens. These larval Derogenes varicus are nearly always found in the region of the ovary of Sagitta, and there is rarely more than one present in each individual, although one may be present at the same time as the larval Ascaris described above. Pharyngora bacillaris (Molin), the second larval trematode found in Sagilta, is a common parasite of the mackerel in its adult state, and has been found in the whiting and also a few other fish, except in the whiting, in an immature state. Nicoll (1914) found many thousand of the im- mature form in Cyclopterus lumpus. These had probably got in with the food and would not come to maturity. The late cercaria stage of this worm was found frequently in medusee (Lebour, 1916) and free in the plankton (Nicoll, 1910). It was also found in ctenophores, so it is evidently not particular as to its intermediate host. Cercarie of all ages were found in Sagitta occupying usually the region of the ovary, as is the case with Derogenes varicus, but sometimes it 1s inside the alimentary canal, which looks as if Sagitta swallows it and afterwards it migrates through the intestinal wall into the region of the ovary. What I have no doubt is the free-swimming cercaria of this trematode was found once in tow nettings on January 28th, 1916. Sagitta from the same samples contained these cercarie without their tails, and it could be traced up to the ordinary Pharyngora late cercaria stage, such as was found in the medusze and free in the plankton. The free-swimming cercaria is extremely interesting (Fig. 6). It is provided with a large tail several times the length of the body and armed with bunches of EXPLANATION OF FIGURES. Fro. 1.—Larval Ascaris from Sagitta x60. A anus, (E cesophagus, Gi.8 blind sac intestine, I.S blind sac from intestine, H boring hook. from cesophagus, B brain, I Fras. 2-3.—Derogenes varicus from Sagitta x 60. Fic. 4.—Ditto containing eggs x 60. Fic. 5.—Free-swimming cercaria of Pharyngora bacillaris < 60. Fre. 6.—Cercaria of Pharyngora bacillaris from Sagitta x 60. O oral sucker, V ventral sucker, E excretory duct, E.P excretory pore, I intestine, P pharynx, VT vitellaria, OV ova. [ 204 ] SOME PARASITES OF SAGITTA BIPUNCTATA. 205 long bristles placed at regular intervals and giving it the appearance of an annelid. The tail is an efficient swimming organ, and the bristles no doubt serve for keeping the whole animal floating. Two large kidney- shaped black eyes are conspicuous, the oral sucker has the typical Pharyn- gora form which is more like a pharynx in shape, the true pharynx leading from it to a short cesophagus and intestinal coeca reaching to the end of the body. The whole body is covered with small spines. In the specimens inside Sagitta the eyes have begun to show diffuse pigment as in the older specimens instead of its being in a thick black mass as in the free-swimming form. Neither Derogenes varicus nor Pharyngora bacillaris have been found encysted, and it is presumed that the encysted stage is omitted as the cercarize develop in Sagittt and the other hosts into a late form which is ready to enter its final host. The first host which presumably is a mollusk is yet to be discovered for both of these trematodes. Two larval cestodes were also found in Sagitta from the Sound, one with four suckers and one with none. These were not identified. It is evident that we have in Sagitta an exceptionally good host for many parasites, and probably further investigation would be amply repaid. LITERATURE. 1851. Busco, W. ‘“ Beobacht, iiber Anat. und Entwickl. Wirbelloser Seethiere,” Berlin, p. 98. 1879. GreEF, R. “Die Hchiuren.” Nova Acta der Ksl. Leop. Carl. Deutschen Akad. d. Naturf. XLI., Pt. II, No. 1. 1916. Lespour, M. V. ‘“‘ Medusz as Hosts for Trematodes.” J. M. B. A., Vol. XI, No. 1. 1858. Leuckart, R. unD PaGENsTEcHER, A. “‘ Untersuchungen iiber niedere Seethiere.” Miiller’s Archiv., p. 559. 1881. Levinsen, G M. R. “ Bidrag til Kundskab om Grénlands Trematodfauna.” Over. K. D. Videns. Selsk. Forh., p. 80. 1910. Nicott, W. “ On the Entozoa of Fishes from the Firth of Clyde.” Parasitology, Vol. III, No. 3. 1914. Nicott, W. “The Trematode Parasites of Fishes from the English Channel.” J.M.B.A., Vol. X, No. 3. 1906. OpHNER, T. “ Die Trematoden des Arktischen Gebietes.”” Fauna Arctica. 206 MARIE V. LEBOUR. 1913. Prerantont, U. “Sopra un Nematode Parassita della ‘ Sagitta’’ e sul suo probabile ciclo evolutivo.” Trans. from TX. Congrés International de Zool. tenu a Monaco, p. 663. 1871.* Uniantn. ‘ Ueber die pelagische Fauna des schwarzen Meeres.” Verhandl. d. Moskauer Freunde d. Natur. 1844. Witt, F. ‘“ Ueber Distoma heroés.” Archiv. f. Naturgesch., Vol. X, p. 348. * Not seen by the present writer. [ 207 ] Post-Larval Teleosteans collected near Plymouth during the summer of 1914. By E. J. Allen, D.Sc., F.R.S., Director of the Plymouth Laboratory. With 8 Figures in the Text. In Volume X, No. 2, of this Journal issued in June, 1914, Mr. R. S. Clark published an account of the post-larval fishes collected during the years 1906 to 1913 with the Petersen Young-fish Trawl in the neigh- bourhood of Plymouth. Similar collections were continued regularly under Mr. Clark’s supervision, with the assistance of Mr. E. Ford and Mr. F. M. Gossen, from April to July, 1914, and two or three hauls were made in August and September of that year. At the beginning of August Mr. Clark joined Sir Ernest Shackleton’s expedition to the Antarctic and left Plymouth in the “ Endurance.” The young fishes had for the most part been picked out from the general material collected by the young- fish trawl by Messrs. Ford and Gossen, and it is this collection of voung fishes which forms the subject of the present report. In drawing up the report I have followed closely the arrangement adopted by Mr. Clark for the earlier material, and it should be regarded throughout as being supplementary to his paper (1914). For most of the important fishes I have given a monthly summary of the number of specimens captured during the whole period 1906 to 1914. which includes both the figures given by Clark and those now added. The average number of specimens taken per haul of the trawl] has also been given for each month. For many reasons, however, these averages cannot claim any great degree of accuracy, but they are, I think, useful as giving a general idea of the relative frequency in the different months. The following sources of error must be borne in mind when drawing conclu- sions from the averages. The duration of the hauls has been in most cases twenty minutes, but there are a few instances where the time was fifteen minutes and a few where it was thirty minutes. The error intro- duced by regarding all the hauls as of equal duration will be so small that it will hardly show in the average figures given. 208 E. Jt ALLEN. A more important error will be caused by the fact that the hauls are not distributed with any uniformity over the whole area. The great majority were, however, made outside the 20-fathom line where the conditions are moderately uniform, but in calculating the averages these have not been separated from the hauls made nearer the shore and in the bays. Some of the hauls were made at the surface, some at midwater, and some near the bottom, whilst some few are night hauls, which seem to yield larger numbers, especially at the surface, than those made during the day. These circumstances will all tend to diminish the accuracy of the averages, but they do not, I think, destroy their more general signi- fieance. : The number of hauls made in each month varies considerably, but from May to September the totals are fairly large (Table IL). The number of hauls made in the different years for any given month, as will be seen from the same table, varies so very much that it is not possible to make reliable comparisons of the frequency of any species from year to year. Another source of error is introduced by the fact that the material of which the young-fish trawl is constructed is not altogether satisfactory, and the size of the mesh often differs considerably in different samples, so that even two new trawls may have different catching powers. With use also the material shrinks badly, the meshes become smaller and the amount of water filtered through the net (and hence the catching power) is greatly diminished. All these circumstances make the numerical results approximate only. Table I gives the list of stations at which hauls were made in 1914. The Chart Area, to which each haul is assigned, is that shown on the chart published in Clark’s Report (1914). O9 ) an POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. W hee HIN Seimt La ome 0% ‘q-W ie TeX W NG TDW ‘Soytut La oueyy 0% W TLIA IT AON W LG AW “SoTtur 2 @ ome Oz WS FTO! xa W WG soprtut Fp Wy Mey 0% Ww % XK “WW MG soput Fp WY oUleY 0G $6 a ‘TITAX ah OGgu So[TU F “HE OME YT 0% ¢ TLS ‘TIAX "Y Nee a: EDT ‘sept G “N ouoysAppay 0% S ‘ ATWAeXe ‘Y OG ages ; EW ‘septum Fp “N euogsAppeL 0% iS SAGX oe Seco - FP “septa FN ouoysAppo 0% W TL AGS PNDX: ‘g oY a SaTIUL & “MVS OUOBSAPPA 0% as TL AGS Be T1TX ~v BGaee ) HW ‘sept $9 “N ouoysAppy 0% W i: Tex a | Ge. a: - EPI “septa 9 “Ni ouoysAppyT 0% 9 ‘ EB ay Ge. 5” EW ‘som Fg “N ouoysAppa 0% § . ADK ‘0 peu. - — gayrut @ “of Aq “N euoysAppa 0% W tA 61 X OK. 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Soi fey OULEN 0G d s TIX] ES W 9% ; : © SoTL 9 “YT oULeYy OG tal PL UA OT aD S 1 9G ; ; ; ' HW ‘S89 7 “yy omey OG W 2.44 = sl 9G ; ; ; ee Nee Te eee cl OG W PEUAGT xT x Tj IZ : ; ; : " goytut Z “Gg Aq “Gf PET oumreyy 0% W « TIA el W GZ . : : : : : Solu GZ “N| “S]T ooory 0Z nei oe TIA a Bi &G ; : ; ; IES TN ANT INE O24 | O% ‘a ONT 3 W OT ; ; ; ; STTUU: ee NI S200 OZ WH es SINE 9 7 G . . : : : * oyu FMA NM ‘SJ 9007 OG 8 PL UAG Balan Z “OG Ob — ; : ° : “Avg puesmeyg 0% g ce TNT S ‘L ie ee CSOT EC ON AQ AN oOIe 0G W : sat Z iL Cpe re fy SOLU ED MCNCN, eure 0% tl Alar = wth OG ; A 3 ; ; ; ota T MN N ourey OG ‘ad pT A'9 aati EA a GE ; ; ' ' “HW ‘89[tr ¢ HNN FUlod 42248 OG ‘dW = NoTaIOXG : a Ee ee) Tce Nato Ite 0G W % PANN ADS Ee Se I¢ : : ' “HW “Seq ZN Aq “ODN JUlOg op Mer OG '§ ne BI MONA IC < — 1g : : ; ' “HW ‘Sour Z OPN QUtog oyMRIg O% S PLUG TATX ce eee ice “£qTROOT] her Pe ‘oye ae ; eS queyQ dap jeqoy, ahs i coareanth madeer en GL [ey Jo “ON ‘(Cure ZY wed OT Woaemgoq) [VY FYStuplu = "FPL “WoyJoq= "gq “AOJVApIU= "J “oowpans="g “SUOLRIAIGGe Jo UoTyeURdxTy ‘SNOLLVLS HO LSIT I ATAVL ALLEN. J. KE. ah ZI BO * ; * aetued HO 0g W PUXUP OO Bi 9G ; ; : * sopttd FN Aq “qf ommEyy 0G. Na zs TUN OrOrdaT W LG * soya g “Ni Aq “Wy ouTeYy 0% W PASC oN al; &G Ce oymbsoyy) solat F °§ AQ “Hf ULB 0Z ‘d s UNV XOR XT “ih 3G soa TE °S Aq “WY OMY 0% ‘d i STDXOXEXCT aa ON : ; "mM Avg puresqiy 0% W i SEENON san Ol i: "gy Avg pueszty 0Z W 3 TEXOONGT 20 hath One ; oy AV pueszIy A, 0G W oh OOK S 8G ; ‘sopra Fp “A\'g euoqsAppy 0% W a TANT os Gg * sapiut Z “Ay Aq “N ouoqsAppa 0% € ‘s TAG a Gg * SoTL Z “Ni oUoysAppo 0G W ; SUNS ‘9 GZ ' * oyrur 7 ft Aq ‘ST N ouoqsAppy 0% ‘q is AXXT S 0 ; "oyun Fy Aq Ww G ouoysAppi 0% W . “AIXXT S 0 ayia Fg ouoqsAppy 0Z W PraAco. Exod (e) QE Z a (jou oymbsoyq) So]lut 9 “a Aq “"N auoysAppyy OG agi sf | OA 10) RE : 7 en oymbsoy) Soy Tu 9 “Gl Aq “N auoysAppy OG “a As a pXONeali 0) Re : : ; * SoTTU 9 “NY Aq “ON auoysA PP, OG IN ‘ XO 0) 8g * sapttt 9 “N Aq “GN euoysAppoy 0 S * Seal a LE ; * salut F “AN ouoysAppy 0% d PLUACo WAXY ‘gore ‘SULOUIy Ut ¥ ‘saynutut = ‘a.ingdro qeyg yydep 1eIOL, ee foneneana Gea ee Nace ‘(Cure zy ‘wed QT Weemyoq) [avy FYStapIM—= "FF “WopJoq—="q “LoFWAM PIU = If ‘QovFINS—="G “STOTPRIASIGGe Jo VOIyeUR[AxG ‘SNOLLVIS 4O LSIT SJ ata Vi POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. 2a Table II, showing the Number of Hauls made with the Young-fish Trawl in each month for each of the years from 1906 to 1914 in which investigations were carried on. MontHity NUMBER oF HAULS. 1906. 1907. 1908. 1909. 1913. 1914. Total. March ~~~. ; oo 2 = = = — 2 April oo 2 ~~ 2 — 3 7 May eo — 4 5 —- 13 30 June AO 2 31 12 23 28 106 July See: 4 10 9 29 38 94 August. = — 9 10 D4 2 75 September : pe bal 77 1 85 October. ; a Tl — — - 13 = 14 November _ — —- -— - 9 —- 9 CLUPEID. As in the previous years the Clupeidz show a very marked maximum frequency in May and the first half of June. A considerable number of specimens have been stained and the vertebre counted. In all cases these have proved to be sprats, and there seems no doubt that the sprat constitutes by far the greater proportion of the specimens taken during the months in which the 1914 material was collected. This is rendered more probable by the fact that the abundance of black pigment in the neighbourhood of the anus, which Ehrenbaum considers to be one of the distinguishing characters of post-larval sprats, was observed in nearly all the specimens examined. Unfortunately im the present state of our knowledge of the early stages of the different species of Clupea, the detection of a few specimens of C. harengus or C. pilchardus amongst the large quantities of C. sprattus which are caught in the young-fish trawl is from a practical point of view impossible, the labour involved in staining and counting the vertebrae of so many specimens being altogether out of proportion to the value of the information which would be gained. NEW SERIES.—VOL. XI. NO. 2. MAY, 1917. M E. J. ALLEN. FABLE SEE RECORD OF CLUPEA SP. No. of haul. Date. Depth. No. Size in mm. Wie 29.1v, 14 B. 74 7-16°5 VI. is M. 13 5-6-11-5 VII. es 8. 62 6-22 VIE (Dy = “Civ k4 M. Very many 9-5-25 VIII. (2) 55 M. 220 9-5-24 EXD): toiy14 M. D4 922-5 IX. (3) 33 8. ) 12-16-5 [X..(5) us B. 80 6-24 XI 19.v.14 S 1 16 XII. x S. 460 6-2-20 XIII. < M. 406 5-5-20 XIV. 25.v.14 M. Very many 8-25 XV. 8 Many thousands XVI. ia S. 9-25 XVII. 3.v1.14 J3y 218 6-7-18-5 XVIII. se B. 415 6-1-18-5 XIX. M 195 6—-19-5 XX. 10,vi.14 S.-M. Very many 10-5-28 OXI Alavi! M.—B. 33 XXIII. 1 B. 80 14-27 XXIV. 16.vi.14 B. vf 14-5-19-5 XXV. . B. 9 12-3-18 ca XXVI. He B. 7 9-17 XXVIII. a M. 34 11-6-20 XXIX, vil B. ) 14-24 XXXT. a M. 5) 1)-5=23-5 ORE: . S. 65 HY-5=25 XOOXTV. 19.vi.14 M 3 8-2-13 XXXV. m M 10 7-2-20-5 OER V A 24 va l4 B. 10 7-7-14-5 XK AVI cs B. 11 7-5-19 XOCX VILL M 26 16 XXXIX. = S 10 7-520 MEL 29 vis B 2 10=13 XLII. ‘ B. 6 9213 XLIV. a, M. 4 9-5-11-5 XLV. “ S. | 9-5 XLIX. 9.vii.14 M.—B. 71 11-5=35-5 Ot POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. 21% TABLE IIT. (continued). No. of haul. Date. Depth. No. Size in mm. ibe 6.vil.14 iB: 6 13-28 ca. ibA le B 9 11-5-19 LII. Ke M. 3 12-21 LITI B. i 19 LIV. 9.vi.14 S. tf 13-5-24 LV. m M. 3 15-16-5 LVI. B: 2 17-19 LVII 2 B. 1 20 LVIII. 5 M. 2 19-5-22 LIX. 15.vu.14 M. 30 13-26 exe - M. 3D 13-29 LXI. 16.vu.14 B. 89 11-26 LXII. x B. 4 12-5-17 LXVII. 22. vii. 14 M. ji Reeelnas LXVIII. a B. 30 CO Sv LXIX. es S. 7 13-21 LXX. € M. 2 9-5-14 LXXIII. 29.vu.14 M. 1 Ling LXXV. 4 iB: 1] 9-35-17 LXXVII. 3 B. 2 10-10-5 LXXVIII. i . M. J 2 LXXXIII. 6 2. ] 19 LXXXIV. - B. 2 21-23 LXXXVII. 4.1x.14 M. 2 20:5-22°3 SYNGNATHID. Only six specimens belonging to this family are present in the material, the small number being due to the fact that most of the hauls were made at considerable distances from the shore. The four hauls in which they occurred were made between Penlee and Rame Head and in Whit- sand Bay, the total depth of water being in all cases not greater than 15 fathoms. TABLE. IV. RECORD OF SYNGNATHUS ROSTELLATUS. No. of haul. Date. Depth. No. Size in mm. XXX. 17.v1.14 B: l 26-5 LXIV. 22..vii. 14 B. It 17-5 LXXX. 29 vii. 14 M. 2 93-30:5 TAX XeXT. 5 M. 2 35-52 216 E. J. ALLEN. AMMODYTID. All the specimens of Ammodytes appear to belong to the same species, which is probably A. lanceolatus, though as Clark (1914) points out, it is difficult to distinguish between the young stages of A. lanceolatus and A. tobianus. Table V. gives the records for 1914, whilst Table VI. gives the monthly totals and averages per haul for all the years 1906-1914 for which records exist. The average shows a gradual rise to a maximum in August and then a sudden drop (ef. Clark (1914), p. 340). TABLE V. REcoRD OF AMMODYTES SP. No. of haul. Date. Depth. No. Size in mm. V. 29.iv.14 B: 5 10-5-29 Val - M. 1 20 Var: S S. | 22-6 TX. 15.v.14 B. 2 draleh XI. 19.v.14 S. 2 12-6, 19 XII. . M. ] 7 XIiJ.a 22.v.14 | 14 XIV. 25.v.14 M. 2 (25783 XVI. r S 3 6-11-5 VEL: 3.v1.14 B 10 9-18 VET: ee B 14 5-6, 12-3-18 XXI. 11.vi.14 M 1 10-6 XXII. = 11.vi.14 M.—-B ] 7-5 XXVI. 16.vi.14 B. ft 8-5—-10-5 XXVII. 5 M. 1 8 ca. XXX. 17.vi.14 M 3 9-23 XXXII. M ] 8 ca XXXIT. x S | 12-5 XXXITI. 19.vi.14 M ] 20-5 XXXIV. M 1 13 XXXYV. - M 7 7-6-12-6 XXXVIT. = -24.-vi.14 B. 4 6-15-5 XXXVIII. a M. 5 55-15 XXXIX. 33 S. 1 10 XLVI. 2.vi.14 S. 1 12-5 XLVIII. f M. 2 9-13 L. 6.vii.14 B. 9 1]-24 POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. 217 No. of haul. Date. Depth, No. Size in mm. IPH 6.vil. 14 Be 3 12-5-18-5 LIT. zm M. 3 23 ca. LIV. 9.viu.14 8. 1 18-5 LVI. af Be 2 12-17-5 LVII. ¢ B. iT 12 ca. LIX. 15.vu.14 M. 7 10-16 LX. a: M. 8 12-23-5 LXI. 16.vu.14 iB: 5 13-7-30 LXII. si iB: 5 15-19:5 LXVI. 22.vi.14 M. lt 12 LXVII. M. 8 8-12-5 LXVIII. r Bs 16 7-14:8 1p. DG i S. 3 9-13 LXXITI. 29.vii.14 M. 2 13-15 LXXIV. M. ] 12 LXXV. = B. 13 6-5-15-8 TABLE VI. AMMODYTES SP. Number of Totaluumber haulsin Number Average Month. of hauls which the of Sizeinmm. number 1906-1914. species specimens. per haul. occurs, March 2 1 1 8-5 0-5 April oe, 6 1 Nes 2p97 <2 May : ; : 30 11 ay 6-29 1-07 June = 06 49 247 55-104 2:3 July : . 94 52 420 5-30 4-5 August. meat 46 506 4-5-25 6-7 September oeexe!) 12 14 5-5-24 0-16 October. 14 0 0 November 9 0 0 GADID A. merlangus L. G. minutus O. F. Miiller. G. luseus L. Gadus pollachius lL. G. Table VII. gives the records of the above species for 1914, whilst Tables VITT. to XI. show the monthly totals and averages of all the records from 1906-1914. The few specimens of G. pollachius taken in 1914 were nearly all taken in April and the first half of May. The maximum frequency for the whole period is in March and April. For the whiting 218 EB. J:cALLEN. (G. merlangus) the maximum is in May, whilst in June specimens of the sizes captured by the young-fish trawl are still fairly numerous. May also shows a distinct maximum for G. Juscus and G. minutus. Specimens of all these gadoids are very infrequent in hauls taken after June. TABLE VII. RECORD OF GADUS SP. G. pollachius. G. merlangus. G. luscus. G. minutus, No. of haul. Date. Depth. No. Sizeinmm, No, Sizeinmm. No, Sizeinmm. No. Size inmm, V. 29.iv.14 B. 2 6-16:5 2 6-6-5 a —- 6 7-14 VI. a M. 2 7-5-10-5 WaT: mf 8. 7 65-13 — — - Walt) 8.vs 14 Me oe = 1 7 ae = i 8-5 IX.(1) 15.v.14 M 4 8-10 103 5-5—-11-5 - TX.(3) A 5S. 6 _ 7-5-9-5 5 8-5—10-2 1X.(5) - B. — — 211 6-5-15 4 6-8 ] 73) XG 19.v.14 M. -- — 10 6-16 — = —_— = xa = S. 3 5-5-9 1 6:5 —- —- 2 7-9 NaI a S. 3 9-6—-13 7-12 5 = 6-9:8 16 §-4-12-3 XIU. - M. oo — 8 20:5—8'3 7 5:-6-6:2 158 5-5-15 XIV. 25.v.14 M. — — 21 7-2-14 ll 6-5-16 34 6-516 XV. 3 NS — = + 8-13 2 8-8:5 23 6-7—-14 XVI. is S. — — 14 = 5-5-18 6 7:8-12:7 89 6-17 XVII. 3.vi.14 B. — — 3 6:3-9:5 4 §-3-8-5 XVIII. PH B. --- —- 24 6-5-1] XIX. 55 M. a. — 6 7-13 XxX. 10.vi.14 S.—M. ] 9-3 —- = XXI. 11.vi.14 M. — — 3 8-5-9-5 1 9-5 — — XXII. 5 M.-B. — — i 8:5 — — 3 6:5 -)iet XOXTTT: 5 B: - 1 7 8 7-6-10 XXV. 16.vi.14 B. — — 1 6 L XXVI. Ss B. — — 4 6-2-16 — — — = XXVIII. 5 B. — — 1 Wt XXX. 17.vi.l4 M. i 5-6 2 8-13-5 XXXII. ae S. a — 4 9-18 — XXXVI. 24.vi.14 B. — — 1 14 XXXVITI. a B. - 1 18 XXXVITI. $3 M. — —_ 2 11-11-5 2 5:3-5:5 — — XLI. 26.vi.14 B. - 25 11-28 XLIV. 29.vi.14 M. = ~-- 1 19 XLVI. 2.vu.14 S. — — 2 25-31 1 1€-2 — — LV. 9.vii.14 M. --- ao I 79) LXVII. 22.vii.14 M. 1 7.2 - — LXVIII. 4 B. 1 8-6 LXXVIT. 29.vii.l4 B. - 1 12-4 POST-LARVAL Month. March April May June July Month. March April May June July August Month. March April May June July August September October November 1906-1914. species occurs. i) v9 specimens. TELEOSTEANS. COLLECTED NEAR PLYMOUTH. 219 TABLE VIII. GADUS POLLACHIUS. Number of Totalnumber haulsin Number Average of hauls which the of Sizeinmm. number 1906-1914. species specimens. per haul. occurs. 2 > 2 3D ie 7 4 46 3°5-16°5 6-6 30 8 21 5-22, 0-7 106 5 20 56-42 0-2 94 2 2 6-7-2 0-01 TABLE IX. GADUS MERLANGUS. Number of Totalnumber haulsin Number Average of hauls which the of Sizeinmm. number 1906-1914. species specimens. per haul. occurs, 2 1) 2, a4 J a 5 ‘5M 3-90-10 7:3 30 24 1009 4-18 33°6 106 66 584 3—40 55 94 10 22 6—52:°5 0-2 eS il il 62 0-01 TABLE X. GADUS LUSCUS. Number of Total number haulsin Number Average of hauls which the of Sizein min. number per haul. 0-4 1:5 0-14 0-01 0-06 0-36 0-1 bho bo <3) K. J. ALLEN. TABLE XI. GADUS MINUTUS. Number of Totalnumber haulsin Number Average Month. of hauls — which the of Size in mm.. number 1906-1914. species specimens, per haul. occurs, March. : 2 2 14 4-5-7 “ April i 5) 11 7-18 1-6 May shuren a oe 20 16 405 4-17. ies June O06 16 116 5-48 et Valve 2etc-} ee, oe Oe 5 5 8-6-B4 0:05 GADID. Molva molva L. During the period 1906-13, eight post-larval specimens of Molva molva were taken in May and twenty-two in June. TABLE XII. Recorp oF Motva MOLVA L. No. of haul. Date. Depth. No. Size in mm. DDE 19.v.14 8. | 10-3 XVI. 25.v.14 8. 2 8-6-1] XxCV LL. 3.v1.14 B. 1 8 XXII. 11.vi.14 M. 2 8:5-10-5 XXVIII. — 16.vi.14 B. 1 8-6 XXXVI. 9 24.vi.14 M. 1 12-5 XUV. -29.v1.14 M. 1 10 ca. L. 6.vil. 14 By ! 20 ca. GADID A. Raniceps raninus L. The single specimen of the lesser forkbeard taken in 1914 was obtained at the end of July. Previous records of post-larve of the species at Plymouth are all due to Clark who obtained eight specimens in August and September, 1913. POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. 221 TABLE XIII. ReEcoRD OF RANICEPS RANINUS L. No. of haul. Date. Depth. No. Size in mm, LXXITI. 29.vii.14 M. ] 8 GADID&. Onos mustelus L. All the post-larval rocklings have been identified as O. maustelus. The differences between the species are not, however, very well defined, and it is possible that a few of the specimens may belong to O. tricirratus BL. or to O. cimbrius L. TABLE XIV. RECORD OF ONOS MUSTELUS L. No. of haul. Date. Depth. No. Size in mm. V.-= 20h 14 iB: 2 4-8-8-5 VII. 55 S. 6 4-5-6-5 IX. (1) 15.v.14 M. 5 6-6-7:3 TX. (3) S | 6-5 WG) oe B | 6 XxX 19.v.14 M 5 5-4—10 XII. s 3 6-1-11 XIII. M 5 5-8-5 XIV. 29.v.14 M 7 5-16 XV. S ») 6-15-6 ade C < 14 6-5-15-5 XVIII. 3.vi.14 B. 2 7-7-5 XIX. s M. 1 6-8 XXII. 11.vi.14 M. i 31 XXII. $ M.-—B. I 28-5 XXIV. 16.vi.14 B. 3 7-25 ROXIE - slifsua.l4 M. 2 5-2 XXXIT. % S. 2 5-5 XXXVITI. =. 24.vi.14 M. 3 5:3-6-5 XXXIX. : S. 1 6-5 XLVI. 2.vu.14 8. 2 6-3-8-5 XLVIII. . M. 1 7 XLIX. 3 M.-B. 1 9-8 XS S11 5.wir14 M. 2 88-31 TX. 2 M. 4 12-32 LXXIUI. = 29.vu.14 M. 1 TD bo bo bo E. J. ALLEN. TABLE XV. ONOS MUSTELUS. Number of Totalnumber haulsin Number Average Month. of hauls which the of Size inmm. number 1906-1914. species specimens. per haul. occurs, April : ; 7 3 9 4-5-8-5 1-3 Vi — ate to 10 45 5-16... be June ic op OG 29 46 2-7-31 O-4 July . : : eS: 14 19 4-2-32 0-2 August. Bee) | 1 4-9 0-01 September . : sy SOD i 1 8 0-01 SERRANID. Roceus labrax Li. (= Labrax lupus Cuv.) One specimen of a larval bass 6 mm. long was obtained in Haul IX. (1), a midwater haul made in the west part of Bigbury Bay on May 15th, 1914. It is well represented by Raffaele’s figure (1888 Tav. IV. Fig. 2), which is reproduced by Ehrenbaum in Nordisches Plankton (1905) as Bigte 7d: LABRID. Labrus bergylta Asc. Labrus mixtus L. Ctenolabrus rupestris L. Young stages of wrasse belonging to three different species occur in the material, but there is some slight doubt as to their correct specific determination. The most numerous of the forms is the one in which the body and the greater part of the tail is covered with many black stellate chromatophores, which, however, cease more or less abruptly behind the anal fin, leaving the hinder end of the tail unpigmented. This form has been figured by Danois (1918, p. 155) and there seems no reason to doubt that he has identified it correctly as L. bergylta. Holt’s figure (1899, Pl. V. Fig. 49) is probably the same species, Khrenbaum (1905, p. 7) having already pointed out that it certainly is not Ctenolabrus rupestris as Holt has named it. The just hatched larva of L. bergylta was described by Matthews (1887), and it is not improbable that the larva described by Hefford (1910, Pl. I. Figs. 8 and 8a) as L. maztus also belongs here. In the present records, as well asin those by Clark (1914), all the specimens in which the body is deeply pigmented, but the hinder portion of the tail is quite free from pigment, have been regarded as Labrus bergylta. A second form is Ctenolabrus rupestris. This is well figured by Ehren- baum (1905, p. 8). The body is free from pigment excepting for a large POST-LARVAL. TELEOSTEANS COLLECTED NEAR PLYMOUTH. 223. post-anal black chromatophore on the body at the hinder end of the anal fin, and one or two chromatophores at the root of the caudal fin. I see no reason to question Ehrenbaum’s identification, which is also accepted by Clark. The third form, of which I give an illustration in Fig. 1, kindly made for me by Mr. E. Ford, has occurred not infrequently in the 1914 material. The distribution of the chromatophores is very constant and characteristic. On the dorsal edge of the body, at the base of the dorsal fin, there are on each side five large black chromatophores which remain in specimens preserved in formalin. One of these, the smallest, lies beneath the anterior end of the dorsal fin, followed by two large ones near the middle of the fin, and finally a pair close together near its hinder end. On the post-anal, ventral edge of the body there is a large chromatophore a little way behind the anus, and two more near the posterior end of the anal fin. A single black chromatophore can generally be seen at the Fie. 1.—Labrus mixtus L. Length 10mm. July 2nd, 1914. base of the caudal fin. In the anterior part of the fish there are two or three large chromatophores on the top of the head, a row of small ones on the mandible, two or three on the ventral edge of the abdomen, and one fairly large one immediately in front of the anus. A line of pigment extends along the dorsal side of the abdominal cavity, extending nearly to the anus. The number of vertebra is 38 or 39, rays of dorsal fin 30 or 31, of anal fin 14 or 15. These numerical characters agree completely with those given by Day for Labrus mixtus, and amongst the British Labridee the only other species in which the number of vertebree is so high is Labrus bergylia, the young stage of which seems to be satisfactorily known. I have little hesitation therefore in regarding Labrus mixtus as the proper name to give to the form we are considering. If that be so the larva described by Hefford (1910) is probably L. bergylta and not L. mixtus as he was inclined to think. Post-larval stages of Labrus bergylta ave most numerous in June and July, a few were taken in May and August, whilst in September they practically disappear from the young-fish trawl material. Ctenolabrus rupestris was most abundant in July. In 1914, the only vear for which the species is recorded, Labrus mixtus was distinctly earlier in appearance than C. rupestris and was most abundant in June. bo bo tee EK. J. ALLEN. TABLE XVI. RECORD OF LABRUS spP. F Ctenolabrus Lid rey . 4 xtus. - I aes bergylta Labrus mixtus rupestris. No. of haul. Date. Depth. No. Size in mm, No. Sizeinmm No. Sizeinmm. EXE) = a15:vl4 1 5-8-7-3 = = —_ = x. 19.v.14 M. 1 6-5 ae XIT. as S. — oa i] 6-6 — —— XIII. oS M. 1 6 — — a= = XIV. 25.v.14 M. 3 5:6-6:3 2 Tees = XV. a S. 4 5:2-6-5 — = = = XVI. 3 8. — — 8:5 a == XVII. 3.vi.14 B. 13 5°3-7:5 6-5 = = XVIII. B. 6 6-7 XIX. 38 M. 1 6-5 XX. 10.vi.l4 S.—M. —- a 2 8-=8:5)) = XXII. l1.vi.l4 M.—B. — — 1 9-2 = = XXIII. 50 B —- — | 8-5 = = XXIV. 16.vi.14 B 1 5-5 — — == = XXYV. B 1 5.5 1 6 — = AXVI. B 1 6 2 6-7-8 XXVII. 53 M 2 6-7-5 XXIX. 17.vi.14 B. 3 6-3-7 XXX. =A M 1 6-5 I 6-5 -—— — XXXIV. 19.vi.14 M 1 7-4 XXXVI. 24.vi.14 B —- — 1 7 = XXXVITI. 3 B as — _- = 6 XXXVIIT. M — -- a — 7-3-8 XLVI. 2.vil. 14 S. 1 oa M. 2 XLII. 29.vi.14 B. _- as l 8-5 : 1 XLVII. 33 S. = | — | CO ao ro to | XLVIIL. + M. 1 5-7 - LEX. eS M.—B. 2 4-5—5-7 1 8-5 == = Te 6.vil.14 B. 2, 5:5-6-5 — —- _ a IEG * B. 1] 4-2-5-6 LII. e M. 1 5-3 LIV. 9.vil. 14 S. 10 5:7-6:°5 LV. A M. 12 - 4-5-7 LVI. 5 B 1 5eca IL IDS 15. vii. 14 M 2 7-8 — _- —- — Ta Xl. 16. vii. 14 B. i 7 Paxee He iB: 1 7 = —- — = LXITI. 22.vi.14 B 1 6-6 LXIV. B 1 8 — — _ -— LXVIII. 5 B. — —— 2 7-7-7 —- — XOX mn S. — == = — 1 8 LX XIII. 29. vii.14 M. 1 6 —— — 1 8-6 LXXIV. cs M. ae = = == 1 9-5 LXXV. Me B. — — a = 1 9-6 TAXGXEXS an M. 1 8 — = 1 8-5 TX OO 12. viii. 14 M. 1 7:5 _- — — — 3 9-5-10 — = 1 LXXXVI. 5 B.—M. POST-LARVAL Month. May . June = July. August September . Month. May June . July . Month. June . July . August Wo. bo Ot TELEOSTEANS COLLECTED NEAR PLYMOUTH. TABLE XVII. LABRUS BERGYLTA. Number of Totalnumber haulsin Number Average of hauls which the of Size in mm. number 1906-1914. species specimens. per haul. oceurs. 30° 8 26 4:5-7°5 0-87 106 42 240 3-25-24 2-2 94 49 348 3-20 37 75 1s) 29 3-10 0-38 85 1 1 4-5 0-01 TABLE XVIII. LABRUS MIXTUS. (1914 only.) Number of hauls in which the Number of Total number of hauls Average Size in mm. number 1914 only. species specimens. per haul. occurs. 13 3 t 6-6-8:-3 0-31 28 8 10 6-5-9-2 0-36 38 3 7 7-10 0-18 TABLE XIX. CTENOLABRUS RUPESTRIS. Number of Totalnumber haulsin Number Average of hauls which the of Size in mm. number 1906-1914. species specimens. per haul. occurs. 106 14 39 3°8-9°8 0-37 94 30 131 4-10 1-4 15 8 3 5-5-9 0-17 CARANGID A. Caranz trachurus L. Only one specimen of the scad or horse mackerel is recorded amongst the 1914 material. This was 23-5 mm. long, with most of the adult characters developed, and was taken in Haul LXXXVII. at midwater off Penlee Point on September 4th. The previous records given by Clark (1914, p. 348) are all for July, August and September. 226 By. ALLEN. SCOMBRIDE. Scomber scomber L. Perhaps the most interesting feature in the material collected with the young-fish trawl in 1914 is the abundance of young stages of the mackerel, which were far more numerous than in any of the previcus years for which records are available, though a number of specimens were taken by Hefford (see Clark, 1914, p. 349) in June, 1906, and June, Wi A Me | Sie a0 7 8 g lon (2 amm. ke 254. bo func dard. pure 10 tt. to 29h. (41 ip Figs 2.—Frequency curve of young mackerel from Hauls X1V.-XTX., caught on May 25th and June 8rd, 1914. Fiq. 3.—Frequency curve of young mackerel from Hauls XX.-XLV., caught June 10th to 29th, 1914. 1908. These young stages were first taken on May 25th, when 22, 29 and 32 specimens were captured respectively in three successive hauls. The numters were still considerable in the hauls on June 3rd. ~ After that date they became less, but the young fish remained in the catches throughout June, whilst isolated specimens were captured in July. The individual fishes were measured, and the results to the nearest POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. Zot ‘5 mm. are recorded in Table XX. Figs. 2 and 3 show in graphic form the length frequencies at each successive half-millimetre for two groups of hauls, the first group comprising XIV.—XIX., taken on May 25th and June 3rd, the second group comprising 16 hauls in which specimens occurred from Haul XX. to Haul XLV., taken between June 10th and 29th. The first group (Fig. 2) shows a definite mode at 6-5 mm. and the Fie. 4.—Scomber scomber L. Length 6mm. May 25th, 1914. Fie. 5.—Scomber scomber L. Length 9mm. May 25th, 1914. Fic. 6.—Scomber scomber L. Length 11-5 mm. May 25th, 1914. 4 Fig. 7.—Scomber scomber L. Length 16 mm. ca. July 22nd, 1914. arithmetic mean is 7-15 mm. ‘The second group (Fig. 3) has two modes, one at 6-5 mm. and another at 9-5 mm., whilst the arithmetic mean is 8-8 mm. It is probable that the mode at 9-5 in the second group (Fig. 3) is due to the group of fish found in the earlier hauls and represented in Fig. 2, which then showed a mode at 65mm. This would indicate a srowth of 3mm. in three weeks. If this interpretation be correct then the other mode in Fig. 3, that at 6-5 mm., would be most easily explained 228 hag. ALLEN: as being due to the offspring of a second shoal of spawning fish appearing ~ some three weeks later than the one whose offspring are represented in Fig. 2. A more detailed analysis of the figures by taking five groups of hauls instead of two, namely, (1) XIV., XV., XVI., (2) XVII., XVIIL., XIX., (3) XX., XXI., XXIT., XXITT., (4) XXIV. —-XXXVIITL., (5) XLITE., XLIV., XLV., and noting that the fifth group comprises hauls taken more to the eastward, that is in the direction of the general Channel drift, than the hauls of groups (1) and (2) confirms the view just expressed, though I have not thought it necessary to reproduce the five curves here, the numbers of fish in each group being rather small. In Figs. 4-7 are given four drawings made by Mr. E. Ford, representing four different stages in the growth of these young mackerel. In these drawings the characteristic distribution of the black pigment, the larval teeth, and the other characters by means of which the species can be distinguished are well shown. TABLE XX. RECORD OF SCOMBER SCOMBER.* No. of haul, Date. Depth. No. Sizes in mm. XIV. 25.v.14 M. 22 2 at 5, 1 at 5-5, 7 at 6, 6 at 6-5, 3 at 7, 1 at 7-5, 1 at 8, 1 at 8-5. CV: 25.v.14 S. 29 1 at 5-5, 2 at ‘ 8 at oa 5 at 7, 4 at 7-5, 2 at 8, 4 at 8-5, 2 at 9, l at 10 XVI. 25.v.14 S 32 1 at 5, 7 at 6, 8 at 6-5, 5 at 7, 3 at 7-5, 1 at-8, 4 at 6-5, Tato 1 at 10, 1 at 11-5 XVII. 3.v1.14 18%, 21 1 at 5-5, 1 at 6, 8 at 6-5, 6 at 7, XVIII. 3.v1.14 B: 10 1 at XIX. 3.v1.14 M. 3 eater, i ab 1-5 leat S-D KX, 10.v1.14 °-S:—M. 3 lat 7, I at 3; Wat 12-5 XXI. 11.vi.14 M. 3 leat me 1 at 9, 1 at 10-5 XXIT. 11.vi.14 M—B. 4 Tat 7-5, 2-at 1, lato: Ds. Ml aes bt le a B 4 1 at a J2at 10: lcat lle MXTV. (Lo.val4 IBY I 1 at 6:5. DeXV EE ~ T6lvirel4 B. 2 1 at 8-5, I at 9:5 XXVIII. 16.vi.14 M 7 lat 5,91 at 6, 2°at°9> 2 atedoy 1a: NXT. | RFvi.14 M. 2 leat by Mat: 8°55: SOX ev S. 2 L at:8, Tat 9% * Measurements to the nearest °5 mm. POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. 229 TABLE XX. (continued). No. of haul. Date. Depth. No. Sizes in mm. XXXII. 19.vi.14 M. 1 1 at 12-5. ROX TV. - *19ovi 4) M. 1 1 at 6°5. XXXVI. 24.v1.14 B. 1 1 at-7. XXXVIT. 24.v1.14 B. 1 1 at 7. XXXVITI. 24.vi.14 M. 11 1 at 6, 4 at 6-5, 2 at 7, 1 at 7-5, Ieatre, at 6:5, leat 9:5: RES -297vi. 14: Bye 2 leat 3:55 2 at! 9-5. XLIV. 29.vi.14 M. 3 1 at-6-5, 2 at 9-5. DOV 229-vi.14 S. 1 1 at 8-5, 2 at. 9, 2 at 9.5, 4 at 10, 2 aueO: 5s leratel2: LX. 15.vu.14 M. 1 lat, 9-5. LXVIII. 22.vu.14 Be i 1 at 16. LXIX. 22.vii.14 S. 1 1 at 8-5. ZEID A. Zeus faber L. One specimen only, 12mm. long, was taken, this being found in Haul LXXXIV., a bottom haul made on July 29th, 1914. For 1913 Clark (1914) has recorded a number of specimens in August and September. PLEURONECTID 2. Pleuronectes limanda UL. Post-larval dates are exceptionally well represented in the 1914 material. Already at the end of April when the collection began 29 and 37 specimens were obtained in one haul. The maximum abundance was reached in May, and in three hauls taken off the Eddystone on May 25th, 290, 276, and 508 individuals were captured. It is worth noting that these three hauls were taken during the dark hours of the night, between 10.25 p.m. and midnight. During June the numbers obtained fell off rapidly and after the 2nd July no more specimens were obtained. During June also the most prolific hauls were made at night. The details of the captures for 1914 are shown in Table XXI., whilst Table XXII. gives monthly summaries of the hauls made during the period 1906-14. Pleuronectes macrocephalus Donov. Although no young merry-soles were taken until May 15th the captures reached a maximum before the end of that month, falling off during NEW SERIES.—VOL. XI. NO. 2. MAY, 1917. Q 230 Hs os ALLEN: June and July, when chiefly the larger sizes were taken. The figures for 1914 are given in Table XXI., and the monthly summaries for 1906-14 in Table XXIIT. The species is more abundant in hauls taken beyond the 20-fathom line. In Table XXIII. this is shown by the figures given for the month of May. The average number of individuals per haul for all the hauls is 6-6, whilst the average for the hauls at and beyond the 20-fathom line ig) 12-2. TABLE XXI. RECORD OF PLEURONECTES SP. No. of P, limanda. P, microcephalus, Haul. Date. Depth. No. Sizeinmm. No. Sizeinmm. Vs 29.iv.14 B. 36 SoA a = == Vii és M. 29 4-5-9-2 == == Val: Es 8. 6 SeSeAOes) = = VIIL.(2) - M eG 0aR ho Gee cae 1X5). 1.4) B 23 5-126 — 3. Gamiaeg Xe: UBB vigle Sell 5) 8-3-14-3 37 5-11 xe 5. 8 9-13:38 22° “G:a—10-5 XII 8. 3D 4-14-8 21 6-8-10-6 XIII 55 M. 70 4-7-12:0 = 5d 6-15 XIIL.a 22.v.14 46 65-13 = == XIV. 25.v.14. M. 290 5-7-15 25 TILT xSVe 5 8 276 5-5—12-5 7 9-6-13-5 SOuk E s 508 5-126 12 75-145 XVII. 3.v1.14 B. 45 6-5-11-5 5 (ES) XVIII. : B. 9 6-8 8 527-5 SeIK é M. ae esuGerS 1 6 0. OG 10.vi.14 S-M. 22 8-2—14-5 3. 9:5=16 XXT. LL vaca Mt 14 8—14-2 3 10-6-14 XXIE i M-B. 31 85-17 11-10-15 -6 XX 2 B. 32 915-6 22 9-14 XXVI. 16.vi.14 B. om 105-16" = it XXVIT. M. 1 10-5 = us BOX VIET. 4 B. 1 12-5 — — XXX. 17.vil4 = 8M. 2 (all = aE LOOUE , S. = = 1 7 XXXVII. 24.vi.14 B. 1 10-2 3 8-12 XLII. 29.v1.14 B: 1 10-5 ar —— XLVI. Z.vu.l4 §. 8 6:-5-17°3 2 12-4-12°7 XLVII. S. 1 8-5 3 11-5-15-2 33 POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. 231 TABLE XXI. (continued). No of P. limanda. P. microcephalus, Haul. Date. Depth. No. Sizeinmm. No. Sizein mm. XLVIITI. 2.vii.14 M. 3 15-5-16 3) 9-18-5 XLIX. Be M.—B. ye 15-5-16-6 a —- TENT: 9.vu.14 B. = _ 2 9-2-11°5 LVII. Fr B. — — 2 9-9-5 LXVIII. 22.vi.14 B -- -- } 8 LXXVIII. 29.vii.14 M. -— os a: 8 Pleuronectes flesus L. occurred in the following hauls:—V. 1 spec. 7 mm., VII. 3 specs. 6:5-8°5 mm., VIII. (1) 2 specs. 8-8°5 mm., VIII. ) 2 specs: 8-8°5 mm., IX. (1) 1 spec. 9 mm., IX. (2), 33 specs; 5°5-10°5 mm. TABLE XXII. PLEURONECTES LIMANDA. Number of Totalnumber haulsin Number Average Month. of hauls which the of Sizein mm. number 1906-1914. species specimens. per haul. occurs. April oN eg 5 86 45-115 12:3 May . ool 20 1371 4—15 45-7 June . : . 106 28 199 1-59-17 lly, July . : : eos 4 5D 17 . 65-42 0-18 TABLE XXIII. PLEURONECTES MICROCEPHALUS. Number of Total number haulsin Number Average Month. of hauls which the of Size in mm. number 1906-1914. species specimens. per haul. occurs. March : b : 2 1 1 6 0-5 April 3 7 0 0 -~ -- May . . ; : 30 10 199 5-15 6-6 May* : : Are es 9 196 515 12°2 June . : : 2 L0G 30 129 5-16 1-2 July . : é 3 94 10 18 7-18°5 0-19 * Hauls where total depth of waiter is 2) fathoms and over. a, E. J. ALLEN. PLEURONECTIDA. Sub.-fam. BoTHIN &. Arnoglossus sp. The records for 1914 are given in Table XXIV. By far the greater number of specimens taken belong certainly to the species Arnoglossus laterna. There were a certain number of doubtful cases, but in no in- stance was I able to feel sure that the specimen should be attributed to A, Thori or A. imperialis. The monthly summaries for the whole period 1906-14 given in Table XXYV. show a maximum frequency in September with an average of 8-3 per haul. The average for August 6-8 is also high. It may be noted, however, that the post-larval Arnoglossus seems to have been more abundant in June, 1914, than it was in that month of previous years, the average for the month being 8-4 in 1914, whilst for the whole period it is only 2:3. TABLE XXIV. RECORD OF ARNOGLOSSUS SP. No. of haul. Date. Depth. No. Size in mm. XI. 19.v.14 De it 5-5 ca. DONE ~ M. 1 5-6 XIV. 25.v.14 M. 5) 5-8:3 XV. Ls 8. a 6:5-8:3 XVI. Ss 8. 12 5-6-7-6 XVII. 3.v1.14 13% itl 5-D-7-5 XVIII. 3 B. 18 4-8 XIX. S M. it 5-2 DOS 10.v1.14 S.-M. i 9-5-11-7 XXI. 11.vi.14 M. 28 6-5-11-2 XXII. i M.—B. 27 7-11 XXII. 5 B. 47 7T-5-12-3 XXYV. 16.v1.14 B. 1 7 XXVI. =e B: 10 3°D-7-3 XXVIT. 5 M. 3 6-3-9 XXX. 17.v1.14 M. 2 6-5 XXXII. M. 18 55-10 XXXIT. 8. 3 6-10 ca. OXOXEDY:: Teva ala: M. 5 6-4-10-8 POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. No. of haul. XXXYV. XXXVI. XXXVII. XXXVIII. XLII. XLII. XLIV. XLV. XLVI. XLVII. XLVIII. XLIX. AG LVI. LVII. LVIII. LIX. LX. LXI. LXII. LXIII. LXVII. LXVIII. LXX. LXXITI. LXXV. LXXVI. DXXVIL. LXXVIII. LXXXIII. LXXXV. Date. 19.vi. 14 24.vi.14 bP) b>) 29.vi.14 29 39 2.vi.14 0s 6.vit. 14 br) 93 9.vn.14 2 99 15.vu.14 bie) 16.vii.14 33 22.vii.14 bP) 33 ” 29.vi1.14 ”? 33 9? 12.viii.14 Depth. M. iB: B. M. BH EH EW EEO EDD eee eS TABLE XXIV. (continued). No. 3 HH Ome BH wR EB oo re bo bo OoUN & & DW = CO pee —_ © Size in mm, 6-5-12:3 6-5-14 |S g 2 —_— Ho Le] ( DH H © &D HT © - Bae Be ANG TABLE XXV. ARNOGLOSSUS SP. Number of Totalnumber hauls in Number Average Month. of hauls which the of Size in mm. number 1906-1914. species specimens. per haul. occurs. Maya ee 80 5 26 > a 83 0:87 June . : , = 06 30 249 3°5-18°5 2-3 [ June, 1914 jn eh 22 235 BS1S5 = §-4] July . : : : 94 4] D2 3°5—23-5 2°5 August : : : 6) 47 5O7T 3—-28:°5 6:8 September . ve 0D 62 708 4-31 8:3 October. ; : 14 2 2 7 0-14 Sub-fam. RHOMBIN 2. Rhombus maximus Will. R. laevis Rond. Seven specimens of R. laevis were taken in 1914 between May and August, and one specimen of R. maximus in July. These records support the conclusion reached by Clark that the spawning season of the brill is earlier than that of the turbot. TABLE XXVI. ReEcoRD OF RHOMBUS SP. R. maximus. R. laevis. No. of haul. Date. Depth. No. Sizeinmm. No. Size in mm. XIV. 25.v.14 M. — — 2 9-8-11-5 XV. 25.v.14 S. — — 2 6-8,6°8 LXX. 22.vu.14 M. — — 1 6-2 LXXVI. =. 29.-wii.14 M. 2 ESO) a <= LXXVIT. 29.vii.14 M. — — il 7 LXV. 12 val M. — — 1 13 Scophthalmus norvegicus Gthr. The records for 1914 (Table XXVIL.) give a distinct maximum of the post-larval stages in May. The numbers remain fairly large until June 11th, after which only a few specimens were taken. This would indicate that the maximum spawning season is a little earlier than Clark (1914) suggests, being probably in April. The hauls containing the largest number of individuals were made south of the Eddystone, where the depths were from 37-39 fathoms. The monthly summary for the period 1906-14 shows an average number of 14-6 individuals per haul for May, and of 5-4 for June (Table XXVIII). POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. TABLE XXVII. RECORD OF SCOPHTHALMUS NORVEGICUS. No. of haul. xe Dele XII. XIII. XIIl.a XV: XV. XVI. XVII. XVIII. XIX. XeX: XXI. XXII. XXIII. ROOT: XXX. XLVI. LVI. LIX. LXVIIT. Month. May . June. July . Date. Depth. No. 19.v.14 M. 69 = S. 44 a S. 68 ee M. 84 22.v.14 — 2 25.v.14 M. 5 ie S. 1 7 5: 6 3.v1.14 B. 45 eB B. 31 e M. 1 10.vi.14 S.-M. 5 11.vi.14 M. 1g 55 M.—B. 16 - B: 2d 16.v1.14 B. i 17.vi.14 M. 1 2.vil. 14 S. 1 9.vu.14 B. 1 15.vu.14 M. 1 22.vi1.14 B. 1 TABLE XXVIII. SCOPHTHALMUS NORVEGICUS. Number of Totalnumber haulsin Number of hauls which the of 1906-1914. species specimens. occurs. 30 14 438 106 39 576 94 16 33 Zeugopterus unimaculatus Bup. Size in mm. 4-2-1] Average Size in mm. number per haul. 412 14:6 3°5-12-2 5-4 4—]] 0-35 bo ie) OU Fourteen specimens of post-larvee one-spotted topknots were taken in 1914. The only previous records are those of Clark, who found three specimens in June and July, 1915. The 1914 records are of specimens taken in May and the early part of June. The species is easily distin- guished from the other topknots. 236 E. J. ALLEN. TABLE XXIX. REcoRD OF ZEUGOPTERUS UNIMACULATUS Gthr. No. of haul, xe 2H XIV. XV: XVI. XVII. XVIII. XXI. XXII. XXIII. Date. 19.v.14 19.v.14 25.v.14 25.V.14 25.v.14 3.v1.14 3.v1.14 11.vi.14 11.vi.14 11.vi.14 Depth. No. De KH bd oo SS eS Size in mm. Zeugopterus punctatus Blainy. In 1914 the post-larvee were much more frequent in May than in June, indeed they practically disappeared after the beginning of the latter month. The maximum frequency for the whole period 1906-14 occurred in April, though the figure is based on too few hauls to be very reliable. It is clear, however, that the species must have its maximum spawning period in the early months of the year. TABLE XXX. RECORD OF ZEUGOPTERUS PUNCTATUS BI. No. of haul. Date. Depth. No. Size in mm. [Xi(b) sale ae 7 x 19.v.14 M. ih 5-8 XI. 19.v.14 8. 1 6-5 XII. 19.v.14 S. 2 8-5, 8.5 XII. 19.v.14 M. 4 6.5-8.5 XII1.a 22.v.14 — 10 5-0-7 LY: 25.v.14 M. 1 7-5 D.Qie 25.v.14 S. 1 8 XVI. 25.v.14 S. 7 8-5-10-2 XVII. 3.v1.14 B. 2 6-5-6-7 OVAL: 3.v1.14 B. it 15) XTX 3.vi.14 M. if 6 SOXTT: 11.vi.14 M. i 7-6 POST-LARVAL TELECSTEANS COLLECTED NEAR PLYMOUTH. 237 TABLE XXXII. ZEUGOPTERUS PUNCTATUS. Number of Totalnumber haulsin Number Average Month. of hauls which the of Size in mm. number 1906-1914. species specimens. per haul. occurs. April a ea 3 16 3-6 2:3 Map ee ee 380 13 44 510-2 15 June . : = LOG 14 27 55-11-69 0-25 Sub-fam. SOLEIN. Solea vulgaris Quens. The majority of the specimens of post-larve of the common sole were taken in May. The number captured was, however, not large and was below that of the thickback sole (S. varzegata). Solea variegata Don. These were taken in considerable numbers during May and a few were also present in June. The maximum number taken in one haul was 48, in marked contrast to S. vulgaris, of which only one specimen occurred in a haul, except in two cases where there were 2 and 4 specimens. Solea lascaris Risso. Only two specimens were found in the 1914 material, taken on the 22nd July. Previous records made by Clark in 1913 are in July, August, and September. Solea lutea Risso. Not a single specimen of S. lutea was recognised in the 1914 material, although in 1913 Clark found a fair number in June, a month which is well represented in the 1914 hauls. 238 No. of haul. Wi Wale 1X.(5) Xe XI. XII. XIII. XII. (a) XIV. XV. XVI. XVII. XVIII. -O-GE XXIII. XXXVII. LXIV. LXV. Month. April May . June . Month. May . June . July . August EK. J. ALLEN. TABLE XXXII. ReEcorD OF SOLEA. S. vulgaris. Date. Depth. No. Sizeinmm. No. Size in mm. No. Sizeinmm. 29.iv.14 B. 1 5-7 — — — — 3 M. 1 7:5 a = ae = 15.v.14 B. 1 7 —_ = _— — 19.v.14 M. 1 6:9 33 4-8-2 — — ee S. — _— 4] 4-9-5 — — a S. — — 21 5-5-9-2 - — a M. — — 48 4-5-10-2 — — 22.v.14. — 1 6-4 11 4-5-8:-5 —- — 25.v.14 M. I 6-6 43 4-2-12-3 — == p S. 2 6:6, 7:7 3 9-2-9-8 — — = 8. 4 6-2-8:7 9 5-9°8 oo 3.vi. 14 B. — — 5 5:3-7:5 — — Fe B. 1 5 — — — — 11.vi.14 M. — — 2 6-4-7 _ — es B. — ~—— 6 6-5-8:5 — — 24.vi.14 B. — — 2 3:6-5-6 — = 22.vii.14 iB: — = — — ] 10:3 a B. — — — — 1 9-6 TABLE XXXIII. SOLEA VULGARIS, Number of Totalnumber haulsin Number Average of hauls which the of Size in mm. number 1906-1914. species specimens. per haul. occurs, i 2 2 5°7—7°5 0-3 30 1 19 4=10-5 0-63 106 5 5 5-8-7 0-05 TABLE XXXIV. SOLEA VARIEGATA. Total number Pies Number Average of hauls aie ia of Size in mm. number 1906-1914. ae ; specimens. per haul. occurs. 30 11 288 412-3 9-6 106 26 170 3-11 1-6 94 3) 4 4-510 0-04 75 4 7 ees 0-09 S. variegata. 8. lascaris. POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. 239 I GOBIIDA. Gobius sp. Crystallogobius nilssoni Diib. and Kor. Aphya pellucida Nardo. Table XX XV. gives the record of all the gobies which have not been specifically determined, and the list probably includes many young stages of both Crystallogobius nilssoni and Aphya pellucida. The larger specimens, probably chiefly belong to Gobius minutus Pall., though other species may be included. Tables XXXVI. and XXXVII. give the records of those specimens, chiefly the larger ones, of Crystallogobius and Aphya which could be determined with some certainty. The separation of the different species has been too incomplete to make it advisable to draw conclusions as to seasonal distribution. TABLE XXXYV. RECORD OF GOBIUS SP. No. of haul. Date. Depth. No. Size in mm. xe 19.v.14 8. 1 13 xa - S. 2 9-5-12-5 Kane ; M. 5 1012-5 XIII.a 22.v.14 — 63 8-14, 24 XY: 205.v.14 M. 13 9-6-13-3 XV. - S. 3 estas XVI. a S. 18 6-D-15 BOXS 10.v1.14 S.-M. 1 14-5 XXII. ll.vil4 M.-B. 6 12-6-14 XXITI. Pn o Tn POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. 247 TABLE XLII. CALLIONYMUS LYRA. Number of Month. esis hauls in ane Size in mm, anne 1906-1914. pees specimens. per haul. March : ; : 2 2 36 =. 25-6 18 April : : ; 7 6 46 2-5-12 6-6 May . a a0) 21 654* 2-5-11 21-8 June . : : Rea G 77 1sg0* 2-14 17:8 July . ee OA 57 933 2:5-13:0 10 August. ; 5 eer) - 43 279 = =—.2-75-13 3°7 September . 2 +85 20 56 4—10 0-7 October. : . +41 1 i! 5 0-07 GOBIESOCID 4. Lepadogaster. Highteen post-larval specimens were obtained in 1914, thirteen of which occurred in July. According to Clark’s records (1914) specimens may occur from June to September. TABLE XLITI. RECORD OF LEPADOGASTER SP. No. of haul. Date. Depth. No. Size in mm. XXIII. 11.vi.14 B. 1 10-5 XLVI. 2.vii.14 S. 5 10-12 XLVII. * 8. 1 11-2 XLVI. ee M. 5) 8-6-11-7 LV: 9.vu.14 M. il 6-5 LVIL. p B. D 755 LIX. 15.vui.14 M. l! 10 LXXXVI. 12.vii.14 B -M. 4 10-11-2 BLENNIID. Probably two species at least are represented in the material, Blennius pholis L. and Blennius ocellaris L., but I have not succeeded in separating them with certainty. The records are shown in Table XLIV. * m. (=many) has been counted as 50, and v.m. (=very many) as 100. The figures for May and June are therefore approximations only E. J. ALLEN. TABLE XLIV. REcORD OF BLENNIUS SP. No. of haul. Date. Depth. No. Size in mm. XOX. 16.vi.14 B. il 6-5 REVAL, . M. 1 7 XOCXVAT: 24.vi.14 IB i D5 XX XIX. a S. if 9 MLV. 2.vil. 14 S. 2 om) XLVITI. A S. 2 8-5-9-5 XLVIII. * M. 1 12-5 1 6.vu. 14 B. 1 6-4 LI. ‘3 B. 1 7:5 LIV 9.vi1.14 S. 1 ea a 6 6-8-5 LV. M it 6 VE, 55 M 2 12-13-5 LXIV.~ 22.vii.14 B 2 17-5 TRV k B. 1 17 LXVIII. . B: 3 i=o:6 LXXIT. 29.vu.14 M 1 12 LXXV. B 1 7 LXXV. . B it 8:5 TaXoX XU . B 1 8 LXXXVII. 4.1x.14 M 4 83-115 Fre. 8.—Lophius piscatorius L. Length 6-2 mm. July 16th, 1914. POST-LARVAL TELEOSTEANS COLLECTED NEAR PLYMOUTH. 249 PEDICULATI. Lophius piscatorius L. One specimen of an early stage, 6-2 mm. long was found in Haul LXIT., taken near the bottom 7 miles west of Rame Head on July 16th, 1914. A figure of this specimen drawn by Mrs. Sexton is reproduced as Fig. 8. The great resemblance of this figure with Emery’s figure, which is repro- duced by Ehrenbaum in Nordisches Plankton, p. 303, Fig. 108, b, and ascribed by both authors to Macrurus, may be pointed out. It seems to me very probable that that figure should really be assigned to Lophius. The larva of Lophius piscatorius is figured by Danois (1918, p. 164, Fig. 319). Ehrenbaum (1905-9) reproduces Agassiz and Whitman’s figures of American specimens. SUMMARY. Table XLV. is perhaps of interest, as showing the composition of the catch obtained with the young-fish trawl at different times of the year. It has been obtained by combining certain groups of hauls made in 1914 in the offshore waters outside Plymouth, all of them being beyond the 20-fathom line. As far as the conditions are concerned therefore the different groups are fairly comparable. The figure given for each species is the average number of specimens per haul for the group. It will be seen that after June the number of species present as well as the average number per haul are both very much reduced. TABLE XLV. AVERAGES PER HAUL IN DIFFERENT GROUPS OF HAULS. XVITI.- LXXIII. LXXXV. X.-XIII. XIV.-XVI. XXIII. XXXV. LXVII. to and S. of S. of W. of to XLI. to LXX; LXXVIIT. LXAXXVI. Eddystone Eddystone Rame Eddystone EddystoneEddystone W. of May 19,’14. May 25,’14. June 3-11, June 19-26, July 22,’14 July 29,’14. Rame 27-39 fms. 35-37 fms. 1914. LOL4, 32-38 fms. 20-35 fms. Aug. 12,14 26-27 fms, 23-39 fms. 26-27 fms. Clupea : : 5 ally v.m. v.m. 1] Tl 2 — Ammodytes : : 0-7 1 4 3 if 3 — Gadus pollachius . ; 2 — — — 0-2 -— — » merlangus . : 6 13 9 0-5 — — -= ‘ minutus. ; 44 47 2 4 0-2 0-2 — 2) luscus : 3 6 0-4 0-3 — — — Molva molva : ‘ 0-2 0-7 O-4 0-2 — — — Raniceps raninus . : = — — —_ 0-2 — Onos mustelus . P 3 9 0-7 0-7 —= 0-2 — Labrus bergylta . : 0-5 2 3 = a 0-2 2 Labrus mixtus . 2 0-2 1 0-7 0-2 0-5 —- — v.m.—=very many. 250 E. J. ALLEN. TABLE XLV. (continued). XVIT.- LXXIII. LXXXY. 5 Se WI ONE. EG ROMUIIE 2.0.0.0)" bP to and 8. of 8. of W. of to XLI, to LXX, LXXVIII. LXXXVI. Eddystone Eddystone Rame Eddystone EddystoneEddystone W. of May 19,'14. May 25,14. June 3-11, June 19-26, July 22,'14.July29,'14. Rame 27-39 fms. 35-37 fms. 1914. 1914. 32-38 fms. 20-35 fms. Aug. 12,’14 26-27 fms. 23-39 fms, 26-27 fms. Ctenolabrus rupestris . — — —- 0-5 0-2 0-5 0-5 Scomber scomber . — 28 7 2 0-5 — — Pleuronectes limanda . 29 358 22 0-2 = — = - microcephalus 34 15 8 0-5 0-2 0:2 — Arnoglossus laterna : 0-5 8 21 3 3 6 ] Rhombus maximus _ = — — — — 0-3 — 5 laevis oo ] 0-3 a= 0:2 0:2 0-5 Scophthalmus norvegicus 66 4 19 — 0-2 a Zeugopterus punctatus . 4 3 0-7 = = = = 53 unimaculatus 0-5 1 1 — — — Solea vulgaris 0-2 2 0-1 -- — — oo » variegata 36 18 2 0:3 a — — Gobius sp. . ‘ ; 2 11 2 2 1 — Crystallogobius nilssoni 39 18 0-6 — 0-2 — Aphya pellucida a 2 2 0-5 —_ 0-2 0-5 Cyclopterus lumpus == — — 0-2 — = = Trigla gurnardus . Sas hs: 40 29 1 — 1 2 ;» hirundo é _ — 0-1 0:3 1 0-2 — Trachinus vipera . = — — 1 5 2 0-5 Callionymus lyra . 3 6 4 35 11 3 3 — Lepadogaster : -_ = — 0-1 -- — — 2 Blennius . ; -_ = — a 0-3 1 0-5 — LITERATURE. 1887. Marruews, J. Duncan.—Note on the Ova, Fry and Nest of the Ballan Wrasse. 5th Ann. Rep. Fish. Bd. Scotland. 1888. RAFFAELE, F.—Mitteil. Zool. Sta. Neapel. VIII. 1899. Hoxr, E. W. L.—Recherches sur la reproduction des poissons osseux. Ann. Mus. d’Hist. Nat. Marseille. Zoologie. T. V. 1905-9. KEHRENBAUM, E.—Eier und Larven von Fischen. Nordisches Plankton, IV. and X. 1910. Hrrrorp, A. E.—Notes on Teleostean Ova and Larve observed at Plymouth in Spring and Summer, 1909. Journ. Mar. Biol. Assoc. EX@p.ale 1913. Danors, E.—Contribution a l’étude systématique et biologique des poissons de la manche occidentale. Paris. Masson et Cie. 1914. CrarK, R. S.—General Report on the Larval and Post-Larval Teleosteans in Plymout!: Waters. Journ. Mar. Biol. Assoc. X. p. 327. [ 251 } On§the Amount of Phosphoric Acid in the Sea-Water off Plymouth Sound. II. By Donald J. Matthews. With one Figure in the Text. In a previous paper* the writer gave the results of the determination of the phosphates in sea-water, by means of Pouget and Chouchak’s reagent, on a number of samples collected between September 13, 1915, and February 5, 1916, at the Knap Buoy, half a mile outside the break- water at Plymouth. The analyses have been continued so as to cover a period of sixteen months and show a large seasonal variation. The method is described in detail in the previous paper, and consists in throwing down the phosphoric acid with iron and an alkali, treating with nitric acid, and determining the amount colorimetrically in the Dubosq apparatus after adding nitromolybdate of strychnine. A few modifications have been made and are described below. In the first place, as the pressure of other work made it impossible to examine all samples immediately after collection, they were sterilised as soon as taken with toluol or chloroform. Toluol was perfectly satis- factory, but the chloroform in some cases threw down a precipitate on standing, and the absence of figures for July, August, November and December, 1916, is due to the loss of samples from this cause. If the sample is allowed to stand without previous sterilisation the phosphates decrease and may be entirely removed in a few weeks. The standard phosphate solution contained 0-003 mg. of P,O; in one cubic centimetre, and was made up in approximately decinormal nitric acid to prevent the growth of moulds. For the precipitation of the iron, sodium carbonate was used instead of ammonia and ammonium chloride ; 1 ccm. of 2 N solution for 1 cem. of iron solution was sufficient to more than neutralise the excess acid of the latter. In some instances the iron precipitate was greasy and was difficult * Matthews, D. J., ‘‘On the Amount of Phosphoric Acid in the Sea- Water off Plymouth Sound.” This Journal, xi., No. 1, p. 122, March, 1916. Day, DONALD J.~MATTHEWS. to dissolve off the paper completely, so the following method was adopted. Five cubic centimetres of strong hydrochloric acid were poured into the beaker in which precipitation had taken place and distributed over the walls to dissolve any iron ; then 10 ccm. of water were added, the beaker was warmed for a few minutes, and the hot dilute acid was allowed to drop on to the filter paper by means of a small pipette provided with a rubber-teat head. The beaker and paper were well washed and the latter incinerated in a platinum crucible; the ash was dissolved in a little strong hydrochloric acid and added to the rest of the solution, which was then evaporated to dryness on the water-bath ; the chlorides were converted to nitrates by evaporation to dryness with 10 ccm. of the dilute nitric acid, taken up in more nitric acid, using 7 ccm. of 25% by volume if the final bulk was to be 50 cem. The analysis was then carried out as described in the previous paper. In an extreme case the dirty residue on the paper was found to contain 0-0024 mg. of P,O;. The origin of the greasy matter is unknown ; it may be due to the drainage from the port, or, on the other hand, it may be the volatile oily substance which so often renders the distillate turbid when sea-water is boiled with an alkah for the determination of ammonia. It was mentioned in the earlier paper that the amount of phosphates found was increased if the water was previously oxidised with a per- manganate. Attempts to find a suitable method for determining this excess phosphorus have been only partly successful. It is necessary to use strong oxidising substances which do not interfere with subsequent operations and are easily purified. In the end the following process was adopted. From 200 ccm. to 400 cem. of the water were evaporated in a porcelain basin holding nearly 200 cem. until the bulk of the salts had separated; then 10 cem. or 20 cen. of strong nitric acid were added, accord- ing to the amount of sample taken, the dish was covered, and heating continued until the evolution of brown fumes had ceased. The cover was removed and the evaporation was continued to dryness; the dish was then heated over an argand burner until the salts were in gentle fusion and the nitrates of the earths were decomposed with evolution of brown fumes. The dish was allowed to cool and the salts were dissolved by warm- ing for an hour with 150 cem. of water and 1 ccm. of strong hydrochloric acid. tron was added and 5 cem. of 2 N sodium carbonate solution and the analysis completed as before. There is danger of the porcelain being attacked unless it is very carefully heated, and unless it is certain that it gives up no phosphates under this treatment it would probably be better to use fused silica basins. The blank on the reagents used in the analyses reported in the previous 1917 1916 AMOUNT OF PHOSPHORIC ACID IN THE SEA-WATER. Nov. Deca warn Oct. Dec. Jan. Nov. nN ae) ~ > = —) —) > > = ‘a4zI7T Aad *O°d fo swunabal/ ip In Water at Knap Buoy, Plymouth Sound. Phosphates 253 254 DONALD J. MATTHEWS. paper was 0-0036 mg. of P,O;. A repurification of the iron, acids, alkali and water reduced it to 0-0026 mg., and a second purification to 0-0021 mg. The blank on the amounts required for the estimation of total phosphorus was at first 0-0066 mg. and afterwards 0-0061 mg. The blanks were determined both by carrying out analyses on distilled water, to which 00300 mg. of P,O; had been added, and also with small amounts of water, the final solution being made up to 10 ccm. and compared in a special small colorimeter tube holding only 10 cem. The results agreed excellently. The determination of the small amounts of phosphoric acid found during the summer presented considerable difficulty. Making the final volume 10 ccm. gave rather discordant results, and it was subsequently found that the closest agreement was obtained between duplicates if enough of the standard solution was added to the sample to bring the content up to about 0-035 mg. of P,O; per litre, the final volume being 50 ccm. This gives a strong colour in a depth of 40 mm. and at the same time avoids the errors which arise when very small volumes of liquid are to be manipulated. The whole of the results obtained by the colorimetric method are given in the following table, and those for phosphoric acid are plotted in the curve ; the figures for February 17th, 1915, have not been used in this case as the sample was by an oversight allowed to stand unsterilised for six days. SURFACE SAMPLES TAKEN AT THE KNAP BUOY. Total P Phosphates. P.O; mg. per litre. calculated Date. G.M.T. S.%,. Found in duplicates. Mean. to P.O; mg. per litre. Seprazios 10/30aim. 34:96 — 0-046 —- S24 55 aan: 34-78 0-042, 0-041 0-0415 — 26) 1145 a.m. 34:43 0-040, 0-034 0-037 — 29 «11.10 am... <34:14 0-040, 0-037 0-0385 = Dec. 2 12.20 p.m. — 0-0484, 0-0435 0-0460 — od on 10250 "a om old G 0-049, 0-047 0-048 = peaks. /lde30ra am: —- 0-044, 0-041 0:0425 — Ge 12.10ip am: 26-20 — 0-043 — ae 200 11, 25%a5m, 29-69 0-058, 0-064 0-061 — Jans 83 11-35-aam.:--- 25:66 0-057, 0-057 0-057 — 14 155 p.m. 33-87 0-0318, 0-0316 = 0-0317 — 18 2.30 p.m. 33:93 ° 0-0336, 0-0348 0-0342 — AMOUNT OF PHOSPHORIC ACID IN THE SEA-WATER. 255 Total P Phosphates. P.O; mg. per litre. calculated Date. G.M.T. 8.%.. Found in duplicates. Mean. to P.O- mg. per litre. Jan. 24 11.20 a.m. 33°42 0-0378, 0-0391 0-0384 == Feb. 5 12.30 p.m. 31-58 0-0507, 0-0414 0-0460 a elt | LO4 cae = 0-0190, 0-0190 — (0-0190) 0-0323 eae. tll Os saci 33°30 0-0371, 0-0343 0-0357 ——= Mar 11.40 a.m. 33-82 as 0-0350 0-039 i eo) Toh acm, 34-54 0-0201, 0-0115 0-0158 — 5p A, a Oe ee 34°54 0-0101, 0-0122 0-O111 0-050 ee 2s bh AD am. 32°18 0-0104, 0:0148 0-0126 0-045 Aprile Ga" 11.55 a.m. 34-40 0-0160, 0-0180 0-0170 0-016 eee LO an, 34:40 — 0-0056 ~- ages) — 34-40 0-0117, 0-0124 0-0120 0-035 May 9 10-50 a.m. 34-16 0-0158, 0-0130 0-0144 0-046 pee. AD am. 34-60 0-0053, 0-0064 0-0058 a June 19 10.45 a.m. 34-90 0-0185, 0-0184 0-0184 0-036 ete 10 45:3. — 0-0230, 0-0248 0-0239 0-038 Sept. 13 noon — 0-0277, 0-0198 0-0238 0-024 Oct: 19 10.45 a.m. ooL08 0-0194, 0-0155 0-0174 0-029 1917 Jan. 10 12.30 p.m. 33°62 0-0435, 0-0448 0-0442 0-049 In the first place it is clear that the results given in the previous paper which were obtained by precipitating the phosphorus with iron and then weighing as phosphomolybdic anhydride are seriously in error, and it was found that molybdic acid was thrown down at the same time. The data of the present table show that there is a large seasonal variation, the maximum being more than ten times as large as the minimum. At first it was expected that the curve would agree with that for the phytoplankton inverted, but this is not the case. Miss Lebour* has made counts of the diatoms at the surface, 5 fthms. and 7 fthms. on 330 samples taken on 110 days at the Knap Buoy from September 21, 1915, to September 18, 1916. The average number in | ccm. for October, 1915, was 17, and in November 9, while in December and in January, February and March, 1916, there were only one or two. The maximum number for the year, 38, occurred in April, 1916, the high value being due to the last week of the month, 45 bemg counted on the 25th and 137 on the 27th. Then a decline set in, with 30 per cubic centimetre in May and only 9 in June. In July there was a rise to 21 and a secondary * Lebour, Marie V., M.Sc., ‘‘ The Microplankton of Plymouth Sound from the Region beyond the Breakwater.” This Journal and Volume, p. 133. 256 DONALD J. MATTHEWS. maximum of 31 in August, followed by a fall to 17 in September. The curve shows that the maximum value for phosphates, 0-061 mg. of P.O; per litre, coincided with the smallest number of diatoms, and also with the shortest days of the year. The phosphates then commenced to fall at once, irregularly at first it is true, to a minimum, of less than one- tenth of the maximum, at the end of April, which coincides with the diatom maximum for the year. The number of diatoms fell off at the beginning of May, while the phosphate minimum continued to the last week of the month. At this period, however, the alga Phwocystis ap- peared in enormous quantities. It was first abundant on April 25, reached its maximum on May 9th and 12th, then declined, and was absent after June 12th. If the decrease in phosphates 1s to be attributed to their removal by alge, as the writer considers to be the case, some other factor must be sought in addition to the phytoplankton. This is probably to be found in the larger alge, such as Fucus, Laminaria and others. Well grown young plants of these are to be found in February, and must by that time have already abstracted considerable quantities of phosphorus from the water. The march of events would then be somewhat as follows. As soon as the young plants of the fixed alge begin to increase the amount of phosphates in the water falls off, and this decline is further hastened by the sudden increase of diatoms at the end of April. In May the diatoms decrease, but the phosphates are kept at a minimum value by the appearance of Phwocystis, and increase at once when this disappears in June. The want of data for phosphates in July and August prevents a further comparison with the figures for diatoms, but another minimum might be expected in August. Phosphate values are also missing in November and December, 1916, but the records for 1915 show an agreement with what might be expected from the diatom figures, that is, a rise from November to December. On January 10th, 1917, the amount of phosphates present was very nearly the mean of the first two figures for the month in the previous year. The Admiralty regulations have made it impossible to obtain water at a distance from the shore. It is by no means improbable that in mid-Channel, beyond the influence of the fixed weeds, the decrease in the phosphates would not be large until much later in the year when the phytoplankton begins to increase. The last column of the table contains some figures for the total dis- solved phosphorus, calculated to P,O;. It is not claimed that they are accurate, but they certainly show that what may be called for the present “ organic phosphorus ” is often high even when the phosphates are at a minimum, though it varies from month to month. The figures for June 27th, 1916, and January 10th, 1917, are probably the most AMOUNT OF PHOSPHORIC ACID IN THE SEA-WATER. 257 accurate, and as the two samples were analysed side by side they are fairly comparable. They show that the total phosphorus may be as high in summer as in winter, but that in summer only a very small part of it may be present as phosphoric acid. The analyses as a whole, how- ever, do not allow more to be stated with certaity than that there is a soluble phosphorus compound present other than phosphoric acid, that it is probably not a lower acid of phosphorus owing to the com- parative difficulty with which it is oxidised, and that it is probably an organic compound. The nature and origin of this ““ organic phosphorus ”’ is, of course, quite unknown. At first it was thought that it might be due to minute organ- isms which pass through a filter paper, and an attempt was made to filter it out by means of candles such as are used for bacteriological work, but this proved impossible as both Doulton and Chamberland filters gave up a considerable amount of phosphates to distilled water passed through them. It is, however, unlikely that it is due to solid particles, as if iron and a relatively large amount of ammonia are added to sea-water so as to produce a bulky precipitate of hydrates of iron, lime, and magnesium, which would almost certainly entangle and stop any suspended matter, the filtrate from this still shows a considerable amount of phosphate after oxidising. SUMMARY. The amount of phosphoric acid in sea-water off Plymouth was at a maximum of 0-06 mg. per litre of P,O, at the end of December, 1915, after which it fell irregularly to a minimum of less than 0-01 mg., which extended from the last week of April to the latter part of May; it then increased again and in January, 1917, reached the same value as the average for the first part of the month in the previous year. This seasonal variation is probably to be attributed to the removal of the phosphates from solution, at first by the fixed algze, and later in the spring by the diatoms and for a short time by Ph@ocystis. There is also present in sea-water taken near Plymouth another soluble compound of phosphorus which can be converted into phosphoric acid by oxidising agents. Abstract of Memoir RECORDING WORK DONE AT :THE PLYMOUTH LABORATORY. The Development of Alcyonium Digitatum, with some notes on the Early Colony Formation. By Annie Matthews, M.Sc. Quart. Journ. Micr. Sci., Vol. 62, Part 1, New Series, 1916. THE above paper is a record of the successful rearmg of Alcyonium larve in tanks at the Plymouth Laboratory. Ripe male and female specimens collected near the Eddystone during the breeding seasons of 1912-13 and 1913-14 spawned in the tank water, and fertilised eggs were collected from which eventually young colonies were obtained. Segmentation gave rise in various ways to a morula, followed by the pre-planula and planula stages. The pear-shaped free-swimming planula eventually settled by the broad anterior end, and the mouth arose at the narrow posterior end subsequent toa general flattening of the settled planula along the long axis. The characteristic eight mesenteries grew out into the ccelenteron on the second day of fixation, followed by the appearance of spicules and eight hollow circumoral tentacles which alternated in position with the mesenteries. ree entrance of food was permitted on the fourth day, after the degeneration of the base of the cesophageal invagination. On the fifth and sixth day of fixation respectively the ventral and dorsal mesenteric filaments were formed, the two being of homogeneous origin, i.e. consisting of endodermic and ectodermic portions developed in different degrees. At the end of the third week the first bud grew as an outgrowth from the basal stolon formed by the solitary polyp. Very young fixed stages were fed with fine plankton, but colonies of two or three individuals or more were successfully fed on larve and single adults from Leptoclinum and Botryllus colonies. The early buds are arranged in circles round the parent, but in colonies of thirty-two individuals budding took place irregularly. A. M. ——s ee [259 | Marine Biological Association of the United Kingdom. Report of the Council, 1915. The Council and Officers. Four ordinary meetings of the Council were held during the year, at which the average attendance was nine. During the Easter Vacation a Committee of the Council visited and inspected the Laboratory at Plymouth. The Association has suffered a great loss during the year through the death of Mr. J. A. Travers, who was for eighteen years its Honorary Treasurer. During his term of office Mr. Travers worked hard in the interests of the Association, and his advocacy of the practical value of the scientific fishery work which was being undertaken did much to ensure the continued progress of our investigations. The Council elected Mr. George Evans, lately Prime Warden of the Worshipful Company of Fishmongers, to succeed Mr. Travers as Honorary Treasurer. The Council desires to express its thanks to the Royal Society for the use of the Rooms at Burlington House in which its meetings have been held. The Plymouth Laboratory. The buildings, fittings and machinery at Plymouth have been kept in a state of efficient repair, but owing to the war all expenditure has been kept at the lowest possible limit. It has been necessary, however, to effect some repairs to the Shone’s ejector, which pumps water from the sea, and the small gas-engine used for circulating sea-water through the Aquarium and Laboratory tanks has been fitted with a new piston and cylinder liner. The Boats. The steamer Oithona has not been put in commission this year. All the collecting work which has been possible has been done with the small sailing boat built for the Association two years ago. The motor boat given to us by Colonel G. M. Giles was sold early in the year for the sum of £35, as there was little prospect of making use of her for some time to come. 260 REPORT OF THE COUNCIL. The Staff. Dr. J. H. Orton and Mr. L. R. Crawshay have joined His Majesty’s Forces for the war, making with Mr. E. W. Nelson and Mr. E. Ford, who joined last year, and Mr. R. 8S. Clark, who accompanied Sir Ernest Shackleton’s Antarctic Expedition, five members of the staff who have been absent this year. Of the old staff, in addition to the Director, Dr. K. J. Allen, only Mr. D. J. Matthews remains, he being employed by the Association for half his time. Miss M. V. Lebour, M.Sc., lecturer in Zoology of the University of Leeds, has been appointed a temporary Naturalist for the period of the war and the Council is indebted to the Senate of the University for granting Miss Lebour the necessary leave of absence. Mrs. D. J. Matthews, M.Sc., has also been engaged for part of her time in carrying out fishery researches for the Association. Mr. D. W. Cutler, B.A., now Lecturer in Zoology at Manchester University, was employed for some months last summer in assisting with fishery work. Those members of the staff who have joined His Majesty’s Forces are being paid by the Association the differences between their salaries and. service pay. Occupation of Tables. The following Naturalists have occupied tables at the Plymouth Laboratory during the year :— W. DE Morean, Plymouth (Protozoa), Dr. E. 8. Goopricg, F.R.S., Oxford (Myxosporidia), Mrs. GoopricH, B.8c., Oxford (Parasitic Protozoa). Miss M. IrwIn, B.A., Cambridge (Embryology of Elasmobranchs). W. O. R. Kine, m.a, Leeds, Ray Lankester Investigator (Temperature coefficient of development of Hehinus miliaris). Mrs. W. O. R. Krye, Leeds (Enzymes of Echinoderm gonads). D, G. Iauuig, B.a., Cambridge (Antarctic Plankton). J. H. Luoyp, Birmingham (Larvee of Nematode of the Common Dogfish in Curcinus menas). Mrs. MarrHeEws, M.sc., Plymouth (Development of Aleyonium), Mrs. E. W. Sexton, Plymouth (Amphipoda and Polycheta), Dr. C. SHEARER, M.A., Cambridge (Dinophilus). The usual Easter Vacation Course in Marine Biology for University students was not held this year. General Work at the Plymouth Laboratory. The number of the Journal issued during the year (Volume X, No. 4) contains a report by Mr. L. R. Crawshay upon his experiments in the keeping of Plankton animals under artificial conditions. Since this paper was written Mr. Crawshay has, after a careful study of the different factors involved, succeeded in rearing Calanus finmarchicus, one of the most typical of the Plankton Copepods, through all stages from the egg to the adult form, under critical experimental conditions. REPORT OF THE COUNCIL. 261 In the same number of the Journal the Director has published a revised list of the Polycheta of the Plymouth District and of the South Devon Coast, with records of the localities in which these annelids have been found. The list contains many new records for the English Channel and several for the British area. The Director has been engaged for a portion of the year in examining a large collection of larval and young stages of fishes made by Mr. Clark and Mr. Ford in the summer of 1914, by the use of Petersen’s young-fish trawl. This work will form the subject of a report on similar lines to those followed by Mr. Clark in his account in the Journal of the young- fish collections of 1913. In connection with a scheme drawn up by the Board of Agriculture and Fisheries for the study of the different races of herrings found around the British coasts, Dr. Orton, with the help of a number of other workers, has examined two large samples of the Plymouth winter herrings, each containing over 500 fishes. This investigation involved the measurement and enumeration of some eighteen characters on each fish. The figures have been sent to the Board of Agriculture and Fisheries for comparison with those obtained from other localities, and in order to make them generally available they are also being published in the Journal of the Association. A series of experiments has been commenced by Mr. D. W. Cutler, with a view to studying the growth of the scales of fishes kept in the Laboratory tanks under different conditions, especially as regards temperature. It is hoped that these experiments may throw some light upon the causes which produce the differences in the lines or markings on the scales now generally used in determining the age of fishes. Mrs. Matthews has taken charge of an investigation on the nutrition and growth-rate of fishes living under Aquarium conditions. Mr. Matthews has been making determinations of the phosphates in samples of sea-water collected at about intervals of one week outside Plymouth Breakwater, in order to study seasonal changes. A consider- able number of analyses have been made, and the results will be pub- lished in the next number of the Journal. The hydrographic work he was previously doing for the Fisheries Branch of the Department of Agriculture, etc. (Ireland), is in abeyance for the present, and since the latter part of October last he has been assisting in the chemical side of the investigations into cerebro-spinal meningitis which are being carried out at the Military Hospital at Stonehouse. The chemical work has been done in the Laboratory of the Association. Miss M. V. Lebour has taken up the study of Plankton, especially that of the most minute organisms which escape from the ordinary silk tow- NEW SERIES,—VOL, XI. NO. 2. MAY, 1917. s 262 REPORT OF THE COUNCIL. nets, but can be obtained by centrifuging samples of sea-water. The samples examined have been taken at frequent and regular intervals during the year by means of a water-bottle, which has been worked at several different depths, generally near the surface, about mid-water and near the bottom, at the entrance to Plymouth Sound. A numerical estimate has been made of the number of organisms of each kind in the individual samples. Miss Lebour has also undertaken the examina- tion of a series of samples obtained by means of tow-nets during the last few years, at fortnightly intervals, at the Seven Stones Light Vessel, midway between Land’s End and the Scilly Islands. Mr. W. O. R. King, assisted by Mrs. King, spent some time at the Laboratory as Ray Lankester Investigator, and continued his work on the temperature coefficient of development of Hchinus. Mrs. EK. W. Sexton has completed a paper on the Mendelian inheritance of eye-colour in the Amphipod, Gammarus chevreuxi, which is being published in the next number of the Journal. Published Memoirs. The following papers, either wholly or in part the outcome of work done at the Laboratory, have been published elsewhere than in the Journal of the Association :— Drury, A. N. The Kosinophil Cell of Teleostean Fish. Journ. Physiology, vol. 49, 1915, pp. 349-366. ARAY, J. Note on the Relation of Spermatozoa to Electrolytes and its bearing on the Problem of Fertilization. Quart. Journ. Mier. Sci., vol. 61, 1915, pp. 119-126. Orton, J. H. An American Enemy of the Knglish Oyster Farmer. Trans. Plymouth Inst., vol. 15, 1912-13 (1915), pp. 247-261. PrxeLi-GoopricH, H. L. M. On the Life-History of the Sporozou of Spatangoids, with Observations on some Allied Forms. Quart. Journ. Micr. Sci., vol. 61, 1915, pp. 81-104. PrxeLni-Goopricn, H. L. M., Minchinia: A Haplosporidian, Proc. Zool. Soe., 1915, pp. 445-457. Ports, F. A, Polychaeta from the North-East Pacific: The Chetopteride. With an Account of the Phenomenon of Asexual Reproduction in Phyllochwtopterus and the Description of Two New Species of Chetopteride from the Atlantic. Proe. Zool. Soe., 1914, pp. 955-994. SVEDELIUS, N. Zytologisch-Entwicklungsgeschichtliche Studien wber Scinaia fur- cellata. Kin Beitrag zur Frage der Reduktionsteilung der nicht Tetrasporenbildenden Florideen. Nova Acta Reg. Soe. Se. Ups., Ser. iv., vol. 4, no. 4, 1915. The Library. The thanks of the Association are due to numerous Government Departments, Universities and other institutions at home and abroad for copies of books and current numbers of periodicals presented to the Library. The list is similar to that published in the Reports of Council of former years. A number of authors have been good enough to send reprints of their papers for the Library and to these also thanks are due. REPORT OF THE COUNCIL. 263 Donations and Receipts. The receipts for the year include a grant from H.M. Treasury of £500, being on account of the war one-half of the sum granted in recent years, a grant from the Board of Agriculture and Fisheries, Development Fund (£500), and one from the Fishmongers’ Company (£600). In addition to these grants there have been received Annual Subscriptions (£136), Composition Fee (£15), Rent of Tables in the Laboratory, in- cluding £25 from the University of London and £20 from the Trustees of the Ray Lankester, Fund (£49) ; Sale of Specimens (£324) and Admission to Tank Room (£99). Vice-Presidents, Officers, and Council. The following is the list of gentlemen proposed by the Council for election for the year 1916-17 :— President. Sir E. Ray LANKESTER, K.C.B., LL.D. , F.R.S. V ice-Presidents. The Right Hon. AustEN CHAMBER- LAIN, M.P. W. Astor, Esq., M.P. G. A. BouLENGER, Esq., F.R.S. The Duke of Beprorpb, K.G The Earl of Ducts, F.R.s8. The Earl of STRADBROKE, C.V.O., C.B. Lord Monraau oF BEAULIEU. Lord WALSINGHAM, F.R.S. A. R. STeEL-Marrnanp, Esq., M.P. The Right Hon. A. J. BALFOUR, M.P., Rey. Canon NorMAN, D.C.L., F.R.S. F.R.S. Epwin WaterHousty, Isq. Members of Council. H. G. Maurice, Esq., c.B. Dr. P. CHALMERS MITCHELL, F.R.S. C. C. Morzey, Esq. F, A. Ports, Esq. C. TatE REGAN, Esq. Prof. D> ARcy W. THOMPSON, C.B. EK. T. Browne, Esq. L. W. Byrne, Esq. Prof. H. J. FLEURE, D.Sc. E. S. Goopricu, Esq., D.sc., F.R 8. Sir EustTack GuRNEY. Prof. J. P. Hit, D.Sc., F.R.8. EK. W. L. Hout, Esq. Chairman of Council. A, E. Surpeiey, Esq., D.Sc., F.R.S. Hon. Treasurer, Grorce Evans, Esq., | Wood Street, London, E.C. Hon. Secretary. E. J. ALLEN, Esq., D.Sc, F.R.S., The Laboratory, Citadel Hill, Plymouth. The following Governors are also members of the Council :— G. P. BrppEr, Esq., Sc.D. W. P. Hasketrr Smitu, Esq. (Prime Warden of the Fishmongers’ Co.). The Earl of PorrsmoutH (Fishmongers’ Company). Sir Ricnarp Martin, Bart (Fish- mongers’ Company). The Hon. NaTHANIEL CHARLES ROTHS- CHILD (Fishmongers’ Company). George Evans, Esq. (Fishmongers Company ). Prof. G. C. BOURNE, D.Sc., F.R.S. (Ox- ford University). A. E. Sureiry, Esq., p.8c., F.R.8. (Cam- bridge University). Prof. W. A. HERDMAN, D.Sc. F.R.S. (British Association). THE MARINE BIOLOGICAL ASSOCIATION Br. Statement of Receipts and Payments for To Balance from Last Year ;— CashPabapamMkerspecn. cacti. waetatocchic chee cotierek eee eaas Cashipineliancieeemee tes ste rere ton todacorec: pain ee eea ee », Current Receipts :— H.M. Treasury for the year ending 31st March, 1916 The Worshipful Company of Fishmongers ............ JNO STN VITO ONO © 5G,50odogdnoaensoaaseopaeneeuonpnadee Rent of Tables (including Ray Lankester’s Trustees, OO UMIVETSibymOl aon dons ico) meine eee cecetce winterest on Investments ms ¢...ccceneet once meereae ements ,, Extraordinary Receipts :— Donstion; Gesell eax ee eccet cote es eat eee Composition Bhleewens pecace. cece ec cneeeie meee acne eater cece Board of Agriculture and Fisheries, Grant from Development Fund for year ending 31st March, ,, Laboratory Boats and Sundry Receipts :— Sales ofeAqparatus te. seeameen acer ete ects cae eten oF PDO CID OT Se cet seaie e ees eae ere lay ene ae aie, Le Oats wNeLSeaG canmetc men: an ansseee see eae Rebate of Insurance,'S.¥. ““Oithona ’)!..2-....5:08. Other Wtemis hic. -a-chacscs cea sesteot eee eee emer The Association’s Bankers hold on its bebalf £410 14s, 8d. New Zealand 4% Stock, 1943-63. 500 0 0 600 0 0 less SC 48 15 0 1411 0 1,298 146 500 0 0 516 5 6 £2,957 19 0 OF THE UNITED KINGDOM. the Year ending 31st December, 1915. Gr. £ 3d. £ GE By Salaries and Wages— Director ince. eee ets sete treee sp aoene Sto atot ee aise eras 300 0 0 Elydrosraphersesse de ee ceo ee sts ceth fon atnceke not 150 0 0 SENlOLUN a UNAS GMaeseasescessesberns der eoeeiee sieves ols gil) 4! JACKS Tha Kaya | a NN, Sepia drictncoae pe ncaa co aR oe OOo aoeaueoR Con 188 14 2 MEMUPOTATY: ye © —ecgpecatseesersaceen osnak cees deo oeiseasoes Di ISS IASSISTAMILE | Ae Sueccecs ccnneeatcoccnon wor gana conan oe ears 61 0 10 55 . (temporary) eecescestuscestatceosesenes ‘2 OG NalariagnanduWacese screecscatccns-cescecusnaaacnesoeee 479 2 7 1;870 8 2 eure vel line xpenses! 3.0, 20. vs.0. ve Pb ces sndeeowanamepatins 1450). 3 Wee lillonacype ss sectact ose secare Conair miscae nase tots ace crkioeey renee 84 4 2 Prcese DUP CALES SOI. sumo ete teen eee see, Seca ee 019 0 GB) i) 45 U@UIAE | isan eaesosuSmop cos aasoacuath Senbeoe ae doaacre menace Cent 2 10a (629 EULESS SANES rane reece eae RO eae ceeeneeatee a Mond: hoasteee encase a? 2h al 89 10 8 », Buildings and Public Tank Room— GassaVWiatersandaCoaligencs se trcscestsctac cas ..cn-e sees C. Preston, H. B., F.Z.S., 53; West Cromwell Road, London, S.W. .......-. Ann Quintin, St. W. H., Seampstone Hall, Rillington, Yorks ........ec0.0000s Ann. Raymond, Major G., The Gymnasium, Western College Road, Plymouth Ann. Regan, C. Tate, F.R.S., British Museum (Natural History), Cromwell IOI, SALAS RSS HaCGAR OR PD OBA SALE a I nascacccoDaEREpoOnoS Sadhietastenas ABO OUCRCG Ann. 1914 UG 1914 1888 1901 1909 1884 1885 1888 1900 1904 1885 #1884 1891 1884 1889 1888 1907 1897 #1899 1890 1884 1906 1903 1910 1891 1884 1884 1910 +1884 1912 1906 1909 1909 1906 1910 1900 1908 1884 1913 1905 1898 1913 LIST OF GOVERNORS, FOUNDERS, AND MEMBERS. Die: Samuel, T. A. S., North Hill House, Torpoint, Cornwall ..........c000000s Ann. Saunders, J. T., B. A.. Christ's College, Cambridge ~...........sssseccssanenees Ann. Savage, R. E., Bote d of Agriculture and Fisheries, Winchester House, DiS tN ONUESIS SOMONE SONA OM Sali ateiacait.|n aaosssageses ialsse\ese0aaaiisiossioae Ann. Scharff, Robert F., Ph.D., Sctence and Art Musewm, Dublin............05. Ann, Schiller, F. W., Butterhall, Stafford ............2-22ceececesescsscesseensseeenee Ann. Schuster, Edgar, D.Sc., 110, Banbury Road, Oxford .......:1..eseseeeeeeee Ann. Selater, W. I:, 10) SloaneiCouns London, SW. 2.2.5. fivc..-.caces so ssese oes Ann. Scott, D. H., M.A., Ph.D., F.R.S., Hast Oakley House, Oakley, Hants.... C. Serpell, E. W., Loughtonhurst, West Cliff Gardens, Bournemouth.......... £50 Sexton, L. E., 3, Queen Anne Terrace, Plymouth ....00..scccrererecconesens Ann. Shaw, Joseph, K.C., Bryanston Square, London, W. ..cccsccsssssceneeneenes £13 Sheldon, Miss lalrans 2g Park, BUdcford. o0, site. 2e-...0 ede sc semoccces cess Ann. Shipley, Arthur E., D.Sc., F.R.S., Christ's College, Cambridge...C. and Ann., £3 3s. Sinclair, William F., 102, Cheyne Walk, Chelsea, S.W..........-c00cesee.0s C. Skinners, the Worshipful Company of, Skinners’ Hall, H.C. ........0.2. £42 Slade, Rear-Admiral Sir E. J. W., K.C.1.E., K.C.V.O., 128, Church SEnCele CONDUCT EL Ua MONON: Vim eaectowe AWacstecs slesire cc Sas coosssesiens sors C. Spencer, Sir W. 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J., Rockvall, Brixham. Sinel, Joseph, 8, Springfield Cottages, Springfield Road, Jersey, CT. Wells, W., The Aquarium, Brighton. a} The Loss of the Eye-pigment in Gammarus cheureuxi. A Mendelian Study. By E. J. Allen, D.Sc., F.R.S., Director of the Plymouth Laboratory, AND E. W. Sexton, F.L.S. With Plates I to VII at the end. CONTENTS. PAGE Section I. ALprino ImMpERrect KyYE ‘ 7 ; 274 Cross A. Albino Female AC x Red Male R.2. Plate I PRG) Cross B. Albino Female AC x Black Male K. A. 278 Constitution of Blacks II, III, 1V and V 278 Ei Reds IT, III, IV and V 284. 35 F, Albinos 286 Section IJ.’ ALL-wHiItE PERFECT EYE . : Cross C. Albino Female AB x White Male R.1. (0 4) J bob bh bo io.) ~I Hypotheses I and II 88 Constitution of Blacks VI, Cross C . 4 ; > 2 9ill Cross-matings is on es s - ; : P ; 4 - 18x08: Constitution of Reds _ ,, te ae : : : : ; : Od sp Albinos ,, 5 : : 5 ; : 3 ; 5 7 Experiments with the Original Stock : ? ; d : : mood The Part-White Eye . é : : ‘ : : : : 5 a) Section II]. No-wuirr Hye. VII ; : : : ; : : gu BAD Section IV. CoLouruess Eyer : j : : ; : : : 5 Bail) Cross between Coloured No-white and Albino . 4 330 Independent Origin of Coloured No-white and Albino No-white or Colourless eyes : : 5 . . . . : : : : . 336 Constitution of the Colourless eye . 6 : ; : : ; . 338 Section V. OneE-Stpep NO-wWHITES : 5 ; : : ; ‘ 5 BB!) SUMMARY ‘ 2 ‘ 3 F : : ; . : ‘ . eros. GENERAL CONSIDERATIONS : 5 : : 3 : ; : ; 5 > ats} EXPLANATION OF PLATES z ; ; L : eee oe : 2 pe a) In a paper by Sexton and Wing (Journ. M.B.A., Vol. XI, No. 1, pp. 18-50) a mutation occurring in the Amphipod Gammarus chevreuri Sexton, was described and figured (PI. I, Fig. 3) in which the usual black NEW SERIES.—VOL. XI. NO. 3. DECEMBER, 1917. ae 274 E. J. ALLEN AND E. W. SEXTON. pigment of the eye was replaced by a bright red pigment.* It was shown that these red eyes behaved as a pure recessive in accordance with Mendel’s law, the hybrid between red-eyed and pure black-eyed animals being black. Certain other mutations which had just occurred were also described and figured in that paper, and it is to a study of these and of others that have since appeared that the present paper is due. Our thanks are due to Miss A. R. Clark, who has given valuable help in the care of the broods and in the examination of the young animals for eye-colour. The system employed for designating the different broods and the individual animals in each brood is as follows: The two original Albino females from which the experiments started are called AB and AC. The five broods obtained from AC are numbered I to V, the one brood from AB is numbered VI. Each animal which came to maturity in each of these broods is designated by a capital letter, A, B, C, ete. Hach brood derived from one of these females is numbered by an arabic numeral, and each animal in the brood is denoted by a small letter, a, b, ¢, ete. Thus I.K.3.a. means the first individual (a) in the third brood (3), of female K from brood I of the original female AC. (See Plate I.) In the plates the colour developed in the eye of each animal is shown by the large circles, and the constitution of the animal in regard to the factors for eye-colour, when known, by the character and position of the small circles. The V-shaped mark indicates that the presence or absence of the factor usually represented in the position where the mark stands has not been proved. In the text the colours are represented by capital letters. A means albino, B black, R red and N no-white. The first letter in a formula in black type gives the visible colour of the eye, the remaining letters the constitutional factors which are carried. Thus B+R+A means a black- eyed animal, carrying the factors for red and albino, B-+-N means a black-eyed animal carrying the factor for no-white. BN and RN mean black and red no-white respectively. SECTION I. THE ALBINO} IMPERFECT EYE The shape of the normal eye of Gammarus chevreuri 1s voter with the margin entire. (Plate VII. Fig. 2.) The eye is raised above the surface of the cephalon, and much rounded, and is composed of numerous * It may be mentioned here that no second case of a red-eyed Gammarus arising independently has occurred up to the present time (September, 1917), all the red-ey ed animals used in the experiments being descendants of the original stock. + The term ‘‘ Albino” is here used to designate those animals in which the eye possesses no coloured retinal pigment, but in which the chalk-white extra-retinal pigment is present. For eyes in which the coloured retinal pigment and the chalk-white extra- retinal pigment are both absent we employ the term “colourless.” LOSS OF EYE-PIGMENT IN GAMMARUS. 219 ommatidia arranged in regular rows, each ommatidium being surrounded by pigmented retinular cells, the pigment being black in the normal eye, red in the mutation. On the surface and around the upper portion of the ommatidia, a chalky white extra-retinal pigment is found, the “accessory pigment,” which gives the reticulated appearance to the ommateum. In the albino eye only this extra-retinal pigment is developed. (Plate VII. Fig. 4.) The ommateum is much altered, is reduced considerably in size, and is very variable in shape, even the eyes of the same animal often differing widely in form, and in the size, shape, number and arrangement of the ommatidia. The surface of the eye is flat, not convex as in the type, with a few ommatidia sparsely scattered, generally around the margin, and with some occasionally lying beyond it. Especially portions of the extra-retinal chalk-white pigment tend to become detached, causing white spots to appear in more or less definite positions on the head. A more detailed study of these spots is still in progress. The Albino eye appeared in the F, generation from a mating of Pure Biack with Pure Red. The young (F,) of this mating all had normal black eyes. The 15 which survived to maturity were kept together in one bowl to breed, each female when ovigerous being removed to a separate bowl until her young were hatched, and then returned to the brood- bowl to mate again. The forty-second brood (F,) obtained from this family consisted of 7 Black-eyed young, 1 Red-eyed and 4 with neither black nor red pigment, the Albino eye just described. The total number of young recorded from all the broods was 745, of which 559 were black- eyed, 182 red-eyed and 4 albino-eyed. The four albinos reached maturity, one male and three females, but only two females survived to produce offspring, the AB and AC (Plate IL) of the following experiments. All the albino-eyed animals used in the experiments are descendants of these, and there has been no other case observed of an independent origin of this mutation. The stock from which these two females came was kept for a further period of eighteen months, and no more albino eyes occurred in it. Cross A. CROSS BETWEEN THE ALBINO FEMALE AC AND A PURE Rep MALE R.2. (Plate I.) One of these females (AC) was mated with a male from Pure Red stock (R.2), the resulting offspring being 3 black and 6 red-eyed young. This at once suggests that colour is dominant to absence of colour, and that the albino eye, in which only white accessory pigment appeared , contained the factors for both black and red retinal pigment. 276 E. J. ALLEN AND E. W. SEXTON. Following Bateson and Punnett we may assume a colour factor C, which with its absence ¢ forms an allelomorphic pair. In the absence of C the factors for black and red in the retinal pigment do not produce any visible effect. The constitution of the pure red male would then be : and of the albino female gee where B and R are the factors for black and red respectively. The mating of these should give in F, :— Cc BR, a black carrying the factor for “red” and also the factor POrealbino. 3% CcRR, a pure red carrying the factor for “ albino.” FA. Generation. Black « Black. The three black-eyed young of this F, generation were 2 females and 1 male (PI. I: I.A.B.C.). The male was mated with the females in turn and three broods were obtained from each. The total number of young was 119, of which 61 were black-eyed, 28 red-eyed, and 30 albino-eyed. Theoretically the cross Cre Bune << © cebu gives gametes CB which with chance meetings would give zygotes :— CB CB CB CB CB CR CoBe dees CHIR Tati Old 8s CR CR CB CR GuB al Gk ec B Cobre acy ase CB CUR Salcombe dene eR Gut Ca ec R CB CReaikacsB | ¢ R That is out of every 16 young there are 9 Black-eyed, viz. :— 1 with constitution C C BB Dees ie Gie-B-B De a CC BR anes se Cie BR * We shall for convenience refer to the factor ¢, which on the hypothesis represents the absence of the colour factor C, as the ‘ albino factor.” bo =I —~] LOSS OF EYE-PIGMENT IN GAMMARUS. 3 Red-eyed, viz. :— 1 with constitution CC RR - io Ce RR 2 4 Albinos, viz. :- 1 with constitution ¢ ¢ BB Ts us ce RR ce BR For 119 specimens the numbers should be according to theory 67 black, 22 red, 30 albino, whilst those found by experiment were 61 black, 28 red, 30 albino, a sufficiently close agreement. y) 4 39 FA. Generation. Red x Red. The six red-eyed young of the F, generation were 4 females and 2 males (Plate I: I.D.E.F.G.H.J.). The males were mated with the females and 875 young were obtained, including a brood of 17 not ex- amined within 48 hours of extrusion.* According to theory the parents all had the constitution CeRR, and these mated together should give : — 3 Red-eyed, viz. :— 1 with constitution CC RR 20s Ce RR 1 Albino ss . eve RR Experiment gave 658 red-eyed and 217 albino,t theory requires 656 red-eyed and 219 albino. FA. Generation. Black x Red. A cross between a red-eyed female and black-eyed male of the F, generation (PI. I: I.B. and D.) gave in three broods 9 black-eyed, 15 red- eyed and 8 albino. Theory requires the proportions 3 black, 3 red, 2 albino, which for 32 young would be 12 black, 12 red, 8 albino. * Unless the young are examined and removed soon after they are extruded a certain number are lost through being eaten by the parents and the more delicate ones tend to disappear first. The albinos seem to be more delicate than the reds, and the reds than the blacks, so that unless the broods are counted within a short time the proportions of the different coloured eyes are liable to error. THE FIGURES GIVEN IN THE PRESENT PAPER INCLUDE ONLY SUCH BROODS AS WERE COUNTED WITHIN FORTY-EIGHT HOURS OF THE TIME OF EXTRUSION, UNLESS THE CONTRARY IS DEFINITELY STATED. + Of these 589 red-eyed and 191 albinos came from the mating of one pair. (1.F. x LE. Plate I, see p. 336). 278 E. J. ALLEN AND E. W. SEXTON. Cross B. CROSS BETWEEN THE ALBINO FEMALE AC, AND BLACK HYBRID MALE K.A. (i.e. a black carrying red). (Plates I and IL.) The albino female that was used in Cross A was also crossed with a black hybrid male, the son of a pure black father by a pure red mother. The result was 7 black and 2 red offspring in the first brood. If the constitution of the albino female is : : and of the hybrid black male as , the result of the cross should be 3 blacks (one pure and two hybrid) and 1 red, all of them carrying the factor for albino. Three further broods were obtained from this cross, the total numbers for all four broods being 75 black, 15 red, a proportion 5 : 1 instead of 3:1, but three of the broods were not counted until some days after extrusion, which probably accounts for the small proportion of reds. F.1. GENERATION. BLACKS. Of the 75 black-eyed young, 49 reached sexual maturity, 27 being males and 22 females. Of these it was possible to test 33 from Broods II, 111 and IV by mating them together or with mates of known con- stitution, and 21 proved to be hybrids, i.e. carried both the factors B and R, whilst 12 were pure black. All without exception had albinos amongst their immediate offspring, or transmitted the character to their descen- dants, showing that both parents possessed the factor c. (Plate I: Broods1l, Ll, LV;: V.) The following list gives the constitution of each individual animal and the different matings made to prove that constitution ; these constitu- tions are shown in detail on Plates I and IT. If.A. Male, Black carrying Red and Albino (Plate IT). Matings :— (1) with female D of the same brood (B+ 4A); 88 young, 65 Black, 23 Albino ; (2) with female VI.A (B+R-+ A); 79 young, 49 Black, 15 Red, 15 Albino ; (3) with a female (B+ R) (from a mating Pure Black with Pure Red); 26 young, 18 Black, 8 Red. I].C. Male, Black carrying Red and Albino (Plate II). Matings :—(1) with female VI.C. (B+R-+ A) ; 115 young, 74 Black, 15 Red, 26 Albino ; (2) with Red No-white female from No-white Stock (previously mated with male VI.A.t.) ; 34 young, 18 Black, 16 Red. LOSS OF EYE-PIGMENT IN GAMMARUS. 279 IJ.D. Female, Black carrying Albino only (Plate IT). Matings :—(1) with male A of the same brood (89 young, 66 Black, 23 Albino).* II.A. Male, Black carrying Red and Albino (Plate I). Mating: (1) with female K of the same brood (B+R-+- A); 61 young, 30 Black, 14 Red, 17 Albino. III.B. Male, Black carrying Albino only (proof obtained by mating the offspring). Matings : (1) with female L of the same brood (B+-A) ; 33 young, 20 Black, 13 Albino. The first brood of this pair were mated together, and also with Red mates ; the resulting young numbered 153, 115 Black and 38 Albino (see Pl. III, Fig. 3, for an example). Black young of the first brood of these were mated together, and gave 19 Black, 3 Albino ; mated with Reds they gave 52 young, all Black. According to these matings both male B and female L are Blacks carrying the Albino factor only. II1.C. Male, Black carrying Albino only (probably). Matings :(1) with female M of the same brood (B+ A, Red factor not known); 78 young, 57 Black, 21 Albino. One of this pair is certainly a (B+ A), the constitution of the other is not known. III.D. Male, Black carrying Albino only. Matings :—(1) with female N of the same brood, (B+ A) ; 115 young, 78 Black, 37 Albino ; (2) with female VI.B.2.e. (R-+A); (19 young, 11 Black, 8 Albino) ; (3) with female IV.X. (R+ 2 young, | Black, 1 Red ; (2) with female O of the same brood, (B+ R-- A); -33 young, 22 Black, 27 hed? 9 Albino. III.H. Male, Black carrying Red and Albino. Matings :—(1) with female Q of the same brood, (B+ R+A); 111 young, 66 Black, 26 Red, 19 Albino. II1.J. Male, Black carrying Red and Albino. Matings :—(1) with female (from wild stock, referred to on p. 329) Black no-white ; 92 young, all Black ; (2) with female 14.b. (of the same stock as male R.1. on Plate II, see p. 324), Pure Red; 14 young, 5 Black, 9 Red. One black-eyed male from mating (1) was mated with an albino female. The first brood of 6 young consisted of 2 black and 4 albino. Hence [I.J. must carry albino. {IL.K. Female, Black carrying Red and Albino. Matings :—(1) with male A of the same brood, (B+ R+ A); (61 young, 30 Black; 14 °Redy1% Albino). III.L. Female, Black carrying Albino only. Matings :—(1) with male B, (B+4A); (33 young, 20 Black, 13 Albino). Proof of male B and this female was obtained by mating broods (see under “ Male III.B’’). | Itl.M. Female, Black carrying Albino. Red not known. Matings :—(1) with male C of the same brood (see note to that animal); (78 young, 57 Black, 21 Albino). III.N. Female, Black carrying Albino. Matings :—(1) with male D of the same brood, (B+ male already mentioned, in order to determine which, if either, of the two hypotheses 1s correct. Taking first the cross between the two blacks, we have :— Hyporuesis I. On the first hypothesis the constitution of the all- white perfect-eyed male will be ~, that of the albino female carrying 2 Paul ( black and red a The gametes for the male will therefore be C only, for the female ¢ B and ec R. The F, zygotes resulting from the mating of these two will be Ce B and Ce R, giving black and red-eyed animals in equal numbers. LOSS OF EYE-PIGMENT IN GAMMARUS. 289 The constitution of the albino imperfect-eyed female is ‘ as already seen on p. 276, that of the hybrid black male with which it was mated is : The gametes are therefore for the male C B and C R, for the female eBandcR. The F, zygotes resulting from the mating of these two will be one Cec B B, a black carrying albino, two Ce BR, blacks carrying red and albino, and one Cc R R, a red carrying albino. If we now cross an F, black from the first of the above matings with an F, hybrid black from the second, we have :— VLA. ?x g¢ILA. CcB x CceBR Female gametes:— CB, C, cB: c Male Q CB. CR, c B, eR ges noes oB |.¢ pepe cleeatae CrB CB GEy) £B | alread ee hee | CR CR CR CR = CB C c B c ec B c B ec B ec B CB c | .¢.B c eR eR cR eR | That is 9 black, 3 red and 4 albino. Hypornesis II. On the second hypothesis the all-white perfect-eyed male is constitutionally a pure red, but the non-appearance of the red is a pathological condition which is not inheritable. Its constitution aN J may then be represented as , and if it is mated with the albino female CR carrying black and red we shall have :— CR 1¢.B OMieic Ey The gametes for the male will therefore be C R only, for the femate eBandc R. The F, zygotes resulting from the mating of these two will be Ce B R and Ce RR, giving black and red-eyed animals in equal numbers. If one of these F, black-eyed animals (VI) is mated with a black from brood If, carrying red, we shall have :— VILA. Oo xc Gi A CcecBRx CcBR NEW SERIES.—VOL. XI, NO, 3. DECEMBER, 1917. U '290 BJ. ATLEN AND: EP Wee SEXONE Female Gametes CB, CR, cB, cR Male =, the same as the female. Pedy goles CBS =0 Bs | OR aE CB CR c B | cR GR .CR | CiRener Pp = (Ceo BB one pure black, with one dose of black only instead of two, and without the albino factor ; (C C B) ; two ,, ,, with one dose of black and with the albino factor ; (Cc B); one black carrying red, without the albino factor ; (CC B R); two =, x So Wal E 5 (Cie -B AR): Under Hypothesis II there would be only four different kinds of black- eyed animals, viz. :— one normal pure black, without the albino factor ; (C C B B) ; two ,, & a avr EB Ks Ag (C ceB BB) two black carrying red, without. ,, Br 55 (CC BR); four ~ % > awit ¥ =e A: (Ces Bik): The difference between the results given by the two hypotheses is that under IT there are no blacks with one dose of black only, their place being taken by additional hybrid blacks. One means of testing the hypotheses, therefore, will be to find out LOSS OF EYE-PIGMENT IN GAMMARUS. 291 by further breeding experiments whether or not the IF, offspring contain blacks with one dose of black. If a one-dose black be mated with another one-dose black the offspring will be all black, if mated with a two-dose black they will be all black, but if mated with a hybrid black (black carrying red) the offspring will contain some red, as we have seen in considering the cross VI.A. IL.A. If we mate together the blacks of the F, generation we obtain in F; some broods which contain red-eyed animals, others which contain only blacks. The parents of the broods containing red eyes will either be two hybrids, or a hybrid and a one-dose black, if the latter exists. If we cross-mate the parents of a number of such broods, in as many different ways as possible, we ought eventually to bring two one-dose blacks together, in which case we should get all black offspring. A second test will be as follows. If a one-dose black be mated with a red it will, according to theory, give blacks and reds in equal numbers, behaving in exactly the same way as a hybrid black. If therefore we take blacks which give red offspring when mated with red, and mate them together, we ought, if the one-dose black exists, to obtain some broods which give all black as the result of two one-dose blacks coming together. By mating together blacks tested with reds in this way, and blacks tested with other blacks and giving red in their broods, we have a further opportunity of bringing together two one-dose blacks (if they exist). These tests have been applied, but we have not been able to find any one-dose blacks, all those tried proving ordinary hybrid blacks, giving both red and black offspring. (See list of cross-matings, p. 303.) Cross C. F.2. GENERATION. BLACKS. The following lists show (1) the constitutions of all the blacks of these broods which have been tested (see Plate II, VI.A and VI.C); and (2) the results of the cross-matings made with blacks which had given some red offspring when mated with either red or black mates :— (1) The Black-eyed young, showing their constitution and the matings by which they were proved. VI.A.l.a. Male, Black carrying the factor for Red only (Plate IV, Figs. 2, 4 and 5). Matings :—(1) with female from Pure Red Stock; 8 young, 5 Black, 3 Red ; \(2) with female | of its own brood, (B+ R+ A); 61 young, 49 Black, 12 Red ; (3) with female of VI.C.l.d. (B+R+A); 42 young, 30 Black, 12 Red. 292, BE. J. ALLEN AND E. W. SEXTON. VI.A.1.b. Male, Black carrying Red only. Matings :—(1) with female from Pure Red Stock; 15 young, 5 Black, 10 Red ; (2) with female g of its own brood (B+ R-+ A); 27 young, 23 Black, 4 Red ; (3) with female f of its own brood, (B+R-+ A) ; 25 young, 17 Black, 8 Red. VI.A.1.c. Male, Pure Black (Plate IV, Figs. 7 and 8). Matings :—-(1) with female from Pure Red Stock, 16 young, all Black ; (2) with female q of its own brood, (R+ A) ; 45 young, all Black. VI.A.1.d. Male, Black carrying Red and Albino. Matings :—(1) with female from Pure Red Stock; 10 . young, 3 Black, 7 Red. (2) (3) (4) (5) with four other females, which 1b ate ; (6) with female VI.B.2.u. (A+R) ; 24 young, 1 Black, 3 Red, 20 Albino * ; (7) with female VI.A.3.q. (B+R+A); 16 young, 10 Black, 2 Red, 4 Albino. VI.A.1l.e. Male, Black carrying Red and Albino. Matings :—(1) with female from Pure Red Stock; 18 young, 11 Black, 7 Red ; (2) with female VI.C.1.h. (B+R) ; 88 young, 60 Black, 28 Red ; (3) with female IV.X. (R+A); 111 young, 42 Black, 42 Red, 27 Albino. VIAL. Female, Black carrying Red and Albino. Matings :—(1) with male from Pure Red Stock; 12 young, 4 Black, 8 Red ; (2) with male VI.C.1.m. (R+ A); 71 young, 31 Black, 18 Red, 22 Albino ; (3) with male b of its own brood ; (25 young, lf Blacks8 Red); (4) with male VI.A.3.c. (B+R-+A) ; 5 young, 2 Black, 1 Red, 2 Albino. * Compare footnote p. 344. The exceptional numbers were specially noted at the time the brood was extruded, and there is no doubt as to the accuracy of the record. LOSS OF EYE-PIGMENT IN GAMMARUS. 293 VLA.1.g. Female, Black carrying Red and Albino. Matings : (1) with male from Pure Red Stock ; 10 young, 5 Black, 5 Red ; (2) with male b, of its own brood ; (27 young, 23 Black, 4 Red) ; (3) with male VI.C.1.m. (R+ A) ; 22 young, 10 Black, 8 Red, 4 Albino. VI.A.1.h. Female, Black carrying Red and Albino. Matings :—(1) with male from Pure Red Stock ; 7 young, 3 Black, 4 Red ; (2) with male o of its own brood, Pure Red ; 31 young, 17 Black, 14 Red. That the female carried the factor for Albino was proved by mating the young of the first brood, when Black, Red, and Albino eyes appeared in the offspring (207 young, 89 Black, 106 Red, 12 Albino). One Red male was also mated with female VI.C.3.e. and one Red male with female VI.B.1.f. and a Black female with male VI.B.2.t. VI.A.1.j. Female, Black carrying Red, albinism not known. Mating :—(1) with male from Pure Red Stock ; 19 young, 7 Black, 12 Red ; VLA.1.k. Female, Black carrying Red only. Mating :—(1) with male from Pure Red Stock ; 17 young, 8 Black, 9 Red. Of the young of this brood 11 survived to maturity ; from their matings in the bowl 77 young have been obtained, 38 Black, 39 Red, but no albino-eyed young have appeared. VI.A.1.1. Female, Black carrying Red and Albino (Plate IV, Figs. 1, 2 and 3). Matings :—(1) with male from Pure Red Stock; 73 young, 39 Black, 34 Red ; (2) with male a of its own brood ; (61 young, 49 Black, 12 Red) ; (3) with male VI.C.1.0. (R+ A) ; 82 young, 37 Black, 24 Red, 21 Albino (and 21 others not examined). Three other black-eved voung were hatched, two died, immature, and the third, a female, which reached maturity was eaten by its mate. 294 E. J. ALLEN AND E. W. SEXTON. VI.A.2.a. Male, Black carrying Red and Albino. Matings :—(1) with female k of its own brood, (A+ B--R); 7 young, 2 Black, 1 Red, 4 Albino ; (2) with female VI.B.3.e. (Pure Red); 20 young, 8 Black, 12 Red. VI.A.2.b. Male, Black, factors carried not known. Mating:—(1) with Red female VI.B.3.¢. ; 5 young, all Black. Both male and female died before mating again; constitution therefore of both unknown. VI.A.2.c. Female, Black carrying Red only. Matings :—(1) with male VI.A.3.h. (B+ Pure Blacks, 5, three males and two females, 2 others, male and female, “ doubtful,” i.e. showing neither the red nor the albino factor in their young nor in the matings obtained from these. Black carrying Albino only, 14, six males and eight females, 3 others, females, “ doubtful,” i.e. no proof of the red factor. Black carrying Red only, 9, three males and six females, | other, female, “ doubtful,” i.e. no proof of the albino factor. Black carrying Red and Albino, 30, thirteen males and seventeen females. In all, 3,137 young were obtained from these matings, 32 of which were not examined for eye-colour. The matings Black by R; by R+A; by A+R, 222 young all Black. Black by B; by B+A; by B+R-+A, 121 all Black. Black carrying Albino, by R; 148 all Black: by R+A; 53 Black and 16 Albino: by A+R, 103 Black, 106 Albino. 2 LOSS OF EYE-PIGMENT IN GAMMARUS. 303 Black carrying Albino, by B+R-+ A, 92 Black, 45 Albino: by A+B-+R, 29 Black, 41 Albino: by B+A, 15 Black, 8 Albino: by B+R, 51 all Black. Black carrying Red, by R, and R+-A, 95 Black, 105 Red. Black carrying Red, by B+R, 29 Black, 14 Red: by B+R-+A, 38 Black, 114 Red. Black carrying Red and Albino, by R, 168 Black, 147 Red: by R+A, 216 Black, 178 Red, 143 Albino: by A+R, 31 Black, 8 Red, 34 Albino. Black carrying Red and Albino, by B+R-+-A, 205 Black, 72 Red, 104 Albino: by A+B+R, 2 Black, 1 Red, 4 Albino. [In the F,, generation proceeded with for proof 450 young (F,) were produced, 272 Black, 147 Red and 31 Albino. | = ‘ (2) List of the cross-matings made with the black-eyed animals which had given some red offspring when mated with reds or other blacks :— VI.A.1.a. Male (B+R): tested with Red: 5 Black, 3 Red. (1) crossed with female VI.A.1.1. (B+R-+A) ; 45 Black, 11 Red ; (2) crossed with female VI.C.l.d. (B+R-+A): 30 Black, 12 Red. VI.A.1.b. Male (B+R): tested with Red: 5 Black, 10 Red. (1) crossed with female VI.A.l.g. (B+R-+ A); 23 Black, 4 Red ; (2) crossed with female VI.A.1.£. (B+R+A); 17 Black, 8 Red. VI.A.1.d. Male (B+R-+ A): tested with Red: 3 Black, 7 Red. (1) crossed with female VI.A.3.q. (B+R-+A) ; 10 Black, 2 Red, 4 Albino. VI.A.1.e. Male (B+R-+A): tested with Red: 11 Black, 7 Red. (1) crossed with female VI.C.1.h. (B+R) ; 60 Black, 28 Red. VI.A.14. Female (B+R-+A): tested with Red: 4 Black, 8 Red. (1) crossed with male b, see above ; (2) crossed with male VI.A.3.c. (B+R+A); 2 Black, 1 Red, 2 Albino. 304 E. J. ALLEN AND E. W. SEXTON. VLA.1.g. Female (B+R-+, 3 reds and | albino. (2) CeRxCcR Male Gametes Cr Oy Chine Female _,, CR, Cave KR, sc Zygotcs CRs ee eR lee CR CR CR CR CR C cR c C C C C CR C ek Cc ec R e R eR en CR C eR c c c € c That is 9 reds and 7 allbivos: (3) COR Cie R Male Gametes CR and C Female __,, a2 JCA (Cx cot." \e Zr eows Gree cR |e | Ca OR Chak aOR. | a | GR C cR Cc | C C (0; ¢ That is 6 reds and 2 albinos. It will be seen that in each case, that is to say, in whatever way the 308 E. J. ALLEN AND E. W. SEXTON. reds in this generation are mated, there would be albinos in the offspring. Further, in each case, in addition to the usual imperfect-eyed albinos cR cB cB all-whites of the same hypothetical constitution as the ek, cB; CR, SiN original “ all-white’ male from red stock - should occur, and if these resemble the original parent they will have perfectly formed eyes. According to Hypothesis II the Reds can also be mated in three different ways. The results would be :— (1) CCR RX OCR R Gametes all C R Zygotes all CC RR. That is, all red. (2) Circ ko ree io kek. Male Gametes CR) cl Female — ,, Can caw Zy gotes CC RR Cicmkik.. © chi Ry -c.cthwk That is, 3 reds and | albino. (3) CCR ARS Ce RR Male Gametes CR Female _,, CR and cR Ly gotes CGR AR andy Cc RoR That is, all red. In two of the instances therefore the offspring would be all red-eyed. in one instance there would be albinos in the brood. Experiment has shown that when reds of the F, generation are mated together some broods consist entirely of red-eyed young, whilst others consist of reds and albinos. Further, the albinos when they occurred were of the usual imperfect-eyed type. Hypothesis II is therefore in agreement with the experimental facts, whilst Hypothesis I is not. The following list shows the Red-eyed young and the matings made to prove their constitution. VI.A.1.m. Male, Pure Red (Plate I). Matings :—(1) with female p of its own brood, (R-+-A) ; 72 young, all Red (Plate IV, Fig. 11) ; (2) with female q of its own brood, (R-+-A) ; 32 young, all Red (Plate IV, Fig. 10) ; (3) with female [IV.O (B+ A); 39 young, all Black ; (4), (5) mated with 2 Albino females: ate them. LOSS OF EYE-PIGMENT IN GAMMARUS. 309 VI.A.1.n. Male, Red carrying Albino. Matings :—(1) with female q of its own brood, (R-+-A) ; 63 young, 52 Red, 11 Albino (Plate IV, Hig. 9); (2) with female VI.B. (R-+A) ; 50 Red, 19 Albino. 69 young, VI A.l.o. Male, Pure Red. Matings : (1) with female h of its own brood (B+R-+ ? > > e > 322 E. J. ALLEN AND E. W. SEXTON. VI.C.3.v. Female, Albino. Constitution unknown. Matings :—(1) with male q of the same brood, (A+R) ; . (30 young, all Albino). All the young died without mating. VI.C.3.w. Female, Albino carrying Red only. Matings :—(1) with male VI.B.3.b. (R+ A); 31 young, 19 Red, 12 Albino. VI.C.3.x. Female, Albino carrying Black and Red. Matings :—(1) with male VI.B.3.c. (R+A); 19 young, 7 Black, 4 Red, 8 Albino. VI.B.1.m. Male, Albino carrying Red. Matings :—(1) with female k of the same brood; no results ; (2) with female VI.B.2.e. (R+ A); 87 young, 50 Red, 37 Albino. VI.B.2.s. Male, Albino. Matings :—(1) with Albino female w of the same brood ; 38 young, all Albino. VI.B.2.t. Male, Albino carrying Red. Matings :—(1) with Albino female u of the same brood ; 70 young, all Albino ; (2) with a female I.K.2.e. (Pure Red); 50 young, all Red ; (3) with female VI.C.3.e. (B+R+A); (28 young, 13 Black, 4 Red, 11 Albino) ; (4) with a female of brood 1 of female VI.A.1.h (B+R); 23 young, 7 Black, 16 Red ; (5) with a female (from a mating in the first brood from male I1.D.1.k.) (Colourless) ; 90 young, all Albino. VE.B.2.. Female, Albino carrying Red. Matings :—(1) with male t of the same brood ; 70 young, all Albino ; (2) with male a of the same brood, (R+ A) ; (48 young, 24 Red, 24 Albino) (Plate PY iio 18). (3) with male VI.A.l.d. (B+R-+A); (24 young, | Black, 3 Red, 20 Albino). VI.B.2.v. Female, Albino carrying Red. Matings :—(1) with male from Pure Red Stock ; 49 young, all Red ; LOSS OF EYE-PIGMENT IN GAMMARUS. Soe Matings :—(2) with male a of the same brood, (R-+A) : (38 young, 35 Red, 3 Albino) ; (3) with a Red male of the same brood which it ate ; (4) with male VI.A.3.h. (B+A); (92 young, 52 Black, 40 Albino) ; (5) with male VI.A.3.e. (Pure Black); (19 young, all Black) ; (6) with male VI.C.2.d. (Pure Black); (21 young, all Black) ; (7) with a Black male from a brood of VI.C.2.dxj.; 2 young, Black. VI.B.2.w. Female, Albino carrying Red. Matings :—(1) with male s of the same brood ; (38 young, all Albino) ; (2) with male b of the same brood (R-— » RN). In this case theory requires that out of 32 young, 9 should be normal blacks, 9 normal reds, 3 black no-whites, 3 red no-whites, 6 normal albinos and 2 colourless (albino no-whites). Fig. 3 shows the first 5 broods with a total of 100 young, the theoreti- cal and experimental numbers for the categories being :— Normal Black = Normal Red Normal pees Blacks. No-whites. Reds. No-whites. Albinos, (Albino No- whites). MOR ys. 57. 5 28 9 28 9 18 6 Bxperment .. 28 15 30 4 20 3 Since the plate was made further broods have been obtaimed, and the total number of young is 491, distributed as follows :— Normal Black Normal Red Normal Colourless Blacks, No-whites. Reds, No-whites. ‘Albinos, (Albino No- whites). IRRCOTY. 3 ¢.<56025 138 46 138 46 9? 30 Experiment .. 109 So 157 45 104 23 F.1. Generation from A+B RN. The young belonging to this generation were mated together and pro- duced 434 young, classified as follows : — Normal Black Normal Red Normal Colour! cas Blacks. No-whites. Reds. No-whites. Albinos. (Albino No- whites), heory sis. 5\<7: 184 61 61 20 82 27 Experiment .. 164 60 66 27 94 23 F.1. Generation from A+R RN. The young belonging to this generation were mated together and pro- duced 220 young, classified as follows :— Red. Red No-white. Albino, Albino (Colcurless) No-white. BG ON Sistas ee Sake 2c 124 41 41 14 Experment, -:.. ... 127 38 42 13 336 ft, J. ALLEN AND E. W. SEXTON, INDEPENDENT ORIGIN OF CoLouRED No-wHitTE AND ALBino No-WHITE oR COLOURLESS EyEs, In the last section colourless-eyed animals were described amongst the grandchildren of the cross Albino eye by No-white eye, and it was shown that these were to be expected according to theory. These animals always had the eye colourless on both sides of the head. Instances of colourless eyes have also occurred in two families amongst the offspring of our original Albino female mated with a pure Red male (Cross A) (Plate I). (1) The Red-eyed male (I.F.) mated with the Red female (I.E.) had a very large number of young, 780 in twenty-six broods, 589 red eyes and 191 albinos (Plate I). Amongst the reds there was a small number of individuals in which the white extra-retinal pigment had become reduced or entirely disappeared, giving rise to the typical Red No-white eye. In 24 animals the white had almost but not entirely disappeared from one or both eyes, only a few small specks of white being discovered with a l-inch power, four on right side, eight on left side, and twelve on both sides. In 14 animals the eye on one side had no white pigment (12 on the right side, 2 on the left), that on the other was normal. In 5 animals the white pigment had completely disappeared from both eyes, the eyes being typical Red No-whites. A similar state of things occurred amongst the Albinos. In seven animals the white pigment had entirely disappeared from the eye of one side (5 on the left side and 2 on the right side), and was present as usual in the eye of the other side. In one animal the white pigment was absent from both eyes, which therefore were quite colourless (see pp. 286 and 339.2). The following are the details of the No-whites in the successive broods :— In Brood 1, one Red-eyed animal had the right eye affected, there being only a fleck or two of white ; when mature the eye was completely no-white. It died without offspring. Another had very thin reticulation in both eyes. (Several of the next generation had hardly any white pigment in their eyes.) In Brood 2, one Red-eyed animal had the right eye completely no-white. In Brood 3, one Albino-eyed animal had the right eye small, and the left eye no-white, i.e. Colourless. (From the mating of two albinos of this Brood 3, 12 young were produced, one of which was Colourless on the right side, and one was Colourless on both sides. In the next generation again, 10 young were obtained from the mating of two of the normal albinos, and one of these again showed the no-white strain, having the right eye Colour- less.) In Brood 4, the animals were all normal-eyed. One Albino, a female, was mated with the Red male from Brood 1, which had very thin white reticula- LOSS OF EYE-PIGMENT IN GAMMARUS, oot tion in both eyes, and in their offspring the no-white strain appeared. (Out of 76 young produced by this pair 38 were Red-eyed, 29 with normal eyes, 3 with one eye normal and the other no-white, and 6 no-white on both sides ; 38 Albinos, 22 of which were normal-eyed and 16 no-white, i.e. Colourless. Two of these young albinos have mated, and had 41 young, 33 normal Albino-eyed and 8 Colourless, which is the usual 3:1 ratio. The Colourless have also had offspring, 8 all Colourless.) In Brood 5, one Red-eyed had the right eye practically no-white, with only a fleck or two of white pigment, left eye normal. (Examined again at maturity the right eye was found to have developed the normal white reticulation, cf. p. 340.4.) One Albino had the left eye Colourless. (In the first brood of 13 young of the next generation one Red-eyed had the left eye no-white, and very little white pigment in the right eye.) In Brood 6, one Red-eyed animal had the right eye no-white, and one Albino had the left eye Colourless. (In the next generation one Red had the left eye no-white, and very little white pigment in the right eye.) In Broods 7 and 8, which were not examined for some days after extrusion, the animals were all normal-eyed. In Brood 9 three Red-eyed animals were affected, one with the right eye, one with the left eye, and one with both eyes no-white ; and two Albinos, one having the right eye and one both eyes no-white. In Brood 10, all the animals were normal-eyed. In Brood 11, one Albino had the left eye no-white. In Brood 12, two Reds had both eyes practically no-white. In Brood 13, one Red had both eyes practically no-white. In Brood 14, three Red-eyed were affected, two had the right eye and one had both eyes no-white. A number of other Reds in Broods 10 to 14 showed a tendency for the white reticulation to break down. In Brood 15 two Red-eyed had the right eye no-white, and one of the two had the reticulation much broken on the left side. Two others had the re- ticulation so much broken, one on the right and one on the left, as to be practically no-white, and in many others the reticulation was very thin. One Albino had the right eve affected, there being only one spot of the white pigment at the upper end of the eye. In Brood 16, two of the Red-eyed had the left eye practically no-white. In Brood 17, three Red-eyed were affected, one with the right eye, and two with the left practically no-white. In Brood 18, one Red-eyed had the nght eye no-white, and one Albino had the right eye no-white, and a very small eye on the left side. In Brood 19, one Red-eyed was no-white on both sides. In Brood 20, all the animals were normal-eyed. In Brood 21, one Red-eyed had the right eye and one had the left eve no- white. In Brood 22, two Red-eyed had hardly any white pigment in the eyes, and one Albino had the left eye Colourless. NEW SERIES.—VOL. XI. NO. 3. DECEMBER, 1917, Z 338 E. J. ALLEN. AND E. W. SEXTON. In Brood 23 all the Red-eyed animals had the red pigment much reduced, giving a yellow appearance to the eyes, and two had the left eye practically no-white. This brood is breeding and has given so far, normal Reds, Red no-whites, one-sided Red no-whites and Albinos. In Brood 24, the red pigment was greatly reduced, only 2 out of 19 Red- eyed showing a faint pink tinge, the others were of a pale yellow tint. Seven of them had hardly any white pigment, and in one of them the right eye was practically no-white. One Albino had the right eye very small. In Brood 25, the coloured pigment in the Red-eyed animals was the normal bright red tint, one had very thin reticulation on the left side, one had the right eye no-white, and very thin reticulation in the left, one had the right eye no-white, with no red pigment in the centre of the eye, two had both eyes no-white. The last Brood, 26, consisted of only three animals, Red-eyed, with the red pigment much reduced. (2) The same Red-eyed male (I.F.) was mated with another Red-eyed female (1.G.) from the same brood as the last and had in 3 broods 46 red-eyed and 18 albino-eyed young (Plate I). The 3rd brood consisted of 25 red and 12 albino-eyed young. These were left together in one bowl, and 15 young were obtained from their chance matings, 4 red, 8 albino and 3 with colourless eyes on both sides. Two of these colourless ones survived, a male and a female (Plate V, Fig. 5). For details of offspring, see p. 339.3. CONSTITUTION OF THE COLOURLESS EYE. That these colourless eyes, whether obtained by breeding together no-whites and albinos (see p. 330) or having an independent origin, behave as recessives to white and to colour is shown by the following results :— 1. (a) A female with both eyes Colourless (C.27, see p. 333), belonging to the F, generation from the mating Albino carrying black crossed with Red No-white, was mated with an Albino male (Plate II, VI.B.2.t.) and produced 108 young in 5 broods all with the usual albino eyes. Two of these broods have reached maturity and from their matings 218 young have been obtained, 163 with the usual albino eyes, and 50 albino no-whites. Theory demands for this number 164 albinos and 54 albino no-whites (Colourless). Some of the albino-eyed young of this second generation have just become mature, and when mated together gave 19 albino-eyed and 5 albino-no-whites (Colourless). (b) From another mating of this kind, Colourless female with Albino male, one brood of 18 young resulted, all with normal albino eyes. These LOSS OF EYE-PIGMENT IN GAMMARUS. 339 mated together have given 106 young, 85 Albino-eyed and 21 Albino no-whites. (c) The first F, brood from F, albinos (A+R+NxA+R-+N) from the family described on p. 336 numbered 55, 45 usual-eyed albinos and 10 albino no-whites, i.e. Colourless. Theory requires 41 albinos and 14 Colourless. 2. A female with both eyes Colourless (AN-+R) (Plate VII, Fig. 6) (whose parents are shown on Plate I, viz. I.E.3.1. 6 and hE3.0. 9 and whose ancestry is discussed on p- 336), the colourless character having originated independently, was mated with a Red No-white male RN descended from F amily VII. The resulting broods are charted on Plate V, Fig. 4, there being 177 young, all with Red No-white eyes. The offspring obtained by mating together individuals from the first brood of these young ones are shown on the plate. In the ten broods figured there were 124 young, 89 Red No-whites (=RN +AN) and 35 Colourless (AN+R). Altogether in this generation we have obtained 481 young, 359 Red No-whites and 122 Colourless. Theory requires 361, e ar. 120 735) From the mating of the first two F » young which matured, a Red No- white male with a Colourless female, 24 young were obtained, RN+- AN 14 and AN-+-R 10. The first mating from the next generation le (RN-+- AN x RN+ AN) produced 14 RN-+-AN and 3 AN-+R. 3. Of the three Colourless-eyed young referred to on p. 338, which arose independently, two survived, a male and a female. These two mated together and the three first broods are shown on Plate V ) Biged: Altogether they produced 85 young, all Colourless (F,). The first brood of these has reached maturity, and mated together these have produced 386 young all with colourless eyes (#',). The first two of these broods are shown on the Plate. Some of these F » broods have just reached maturity, and in chance matings within the brood have produced 10 young, all Colourless (F;). SECTION V. ONE-SIDED NO-WHITES. ANIMALS WITH ONE KYE NORMAL AND THE OTHER ABNORMAL. A number of instances have occurred in which the eye on one side of the head was normal, whilst that on the other was either a coloured “no-white ” eye or a colourless eye, 1.e. an albino “ no-white.” In most cases these animals died before maturity, so that up to the present, we have never had males and females mature at the same time, to breed together. 340 E. J. ALLEN AND W. E. SEXTON. We have therefore mated the few one-sided no-whites which survived with normal-eyed animals and with typical no-whites. The details of the experiments are as follows :— 1. Red female, No-white on the Left side, the white reticulation rather broken on the Right side, mated with a Red no-white male (Plate VI, Fig. 4). This female is descended from the B+R-+ A female, VI.A.1.h. (p. 293), which was mated with a Red male from Pure Red Stock, and gave a brood of 7 young, 3 Black and 4 Red, hatched on May 18, 1916. On examining the brood, August 18, 1916, two Black females and three Red males were found with 25 young (6 Black and 17 Red), 23 of which were normal-eyed, and two, a Red and a Black (see 4), were no-white on the Left side. The Red one was again examined on reaching maturity and the Left eye was found unchanged, still no-white. It was mated with a Red no- white male (i.e. one practically normal eye, to three no-white eyes), and produced 20 young, all with normal Red eyes (R+N). These young were mated together and gave a total of 490, 365 Red- eyed, and 125 Red no-whites. In each animal both eyes were of the same type. The results therefore are in full agreement with the Mendelian theory of the dominance of the white pigment, the numbers required by the theory being 367 Red-eyed to 122 Red no-white. 2. A Black female from Pure Black stock (p. 329) with the Left eye no-white, and very little white reticulation in the Right eye, mated with a No-white male from the same stock and had 15 young, all with normal Black eyes. 3. An Albino female with the Left eye no-white, i.e. Colourless. Parent- age, Albino male carrying Black (A+B) from Brood | of III.B (p. 279) and Red female IV.Y (p. 285). The female was mated with an Albino male, the eyes of which were very small and the shape of the head ab- normal on both sides; 271 young were produced, all with the usual Albino eyes and head shape normal. From 3 pairs of these young mated within the brood 122 offspring were obtained, 121 being normal albinos and 1 being colourless on the left side and normal albino on the right, exactly resembling the grandmother. 4. It may be interesting to add here the account of the young Black female referred to in paragraph 1, above, and of the same parentage as the Red female described. When hatched the Left eye was no-white, and the Right eye had only one streak of white in it. It was examined again at maturity and it was LOSS OF EYE-PIGMENT IN GAMMARUS. 341 then found that the Right eye had developed the normal white reticula- tion, and the left eye had the upper half with the white reticulation, the lower half no-white. Mated with a Red no-white male, it had 64 offspring B+R-+N 31 and R+N 33, all with normal eyes. Two pairs of these have produced young; the first pair, Black with Red, had 83 young, 45 Black, 4 Black no-white, 24 Red, 10 Red no- white ; and the second pair, Red (R+N) with Red (R+N), gave 53 young, 39 Red, 14 Red no-white, none showing any variation from the normal types. These Red F, young are now mature, and their matings Red no-white by Red no-white have given 13 Red no-white, and Red (R+N) by Red no- white have produced 26 young, 11 Red and 15 Red no-white. SUMMARY. Sections I and II. Amongst the stock of Gammarus chevreuxi which had been kept under Laboratory conditions for at least two years a small number of animals appeared in which the coloured retinal pigment was absent, whilst the white extra-retinal pigment remained. The experiments described in the present paper have shown that these eyes were of two different kinds. Eyes of the first kind were derived from a stock which originated in a cross between Black-eyed and Red-eyed animals, and were degenerate and irregular in shape. Four animals of this kind appeared in one brood, and such eyes have since been seen only in direct descendants from these. Hyes of this kind were found to behave as simple Mendelian recessives to eyes showing coloured retinal pigment, whether that pig- ment was red or black, and they are referred to in this paper as “ albino ” eyes. Eyes of the second kind were derived from a pure red-eyed stock, and were perfect in shape. The absence of coloured pigment has been shown not to be inherited, and the one animal of the kind experimented with, when mated with a female of the first kind, gave all coloured offspring. By a study of the descendants of these coloured offspring it has been shown that the parent animal behaves in inheritance exactly as if it were one with normal red eyes. In the course of this investigation all possible crosses have been made between Black-eyed, Red-eyed and Albino-eyed animals. In this way 4 different kinds of black-eyed animals were produced, viz. pure black, black carrying albino, black carrying red, and black carrying red and albino; 2 different kinds of red-eyed animals, viz. pure red and red carrying albino ; 3 different kinds of albinos, viz. albino carrying black, albino carrying red, and albino carrying black and red. 342 E..J.: ALLEN AND EB. W. SEXTON. The figures given below show the number of offspring obtained in our experiments by mating together animals of the constitutions specified in each heading. These are summary figures, giving the totals for all crosses of each particular kind, and include many cases which are not referred to in the previous sections of the paper. The figures demanded by theory are placed below those given by our experiments. The total number of animals of which both eyes were examined for eye-colour to Sept. 8th, 1917, is 26,553. The figures are arranged in the following order under the different eye-colours :— 1. The matings giving offspring all of one colour ; 2. Those giving offspring of two colours in the proportion 3: 1 ; 3. Those giving offspring of two colours, half of one and half of the other ; 4.-7, Those giving offspring of three colours. 1. Matings giving normal-eyed* offspring all of one colour. Black, offspring all normal-eyed Black in appearance, in agreement with theory. Number of young, Black-eyed, BxB 215 Bx B+R 146 BxB+A 87 BxB+R+A 17 BxR 618 BxR+A 126 BxA+B 18 BxA+K 19 B+RxB+ Ds Number of young. Black-eyed. Red-eyed. Albino-eyed. B+R+AxR-+A Experiment 235 169 144 Theory 205 205 137 It will be noticed that in both this and the preceding instance the pro- portion of total coloured (red and black combined) to albino is in good agreement with the Mendelian theory. In each case, however, the experiment gives a great excess of blacks over reds, whereas theory re- quires equality in each case. The numbers are fairly large and it is possible that this result may have some significance. Section III. Animals occurred in which the chalk-white extra-retinal pigment of the eyes was absent. These we have called ‘‘ no-whites.” This mutation appeared independently in several different stocks, and there is evidence that it may be produced in a series of steps or stages, the white pigment being gradually reduced in amount. In some cases the two eyes of the same animal differ in respect to the presence or absence of white pigment, or in the amount of white pigment. The “ no- white ” eye behaves in inheritance as a simple Mendelian recessive to the presence of white. The following numbers are derived from the experiments made with these animals, including also the experiments made with the Albino no-whites (AN) or Colourless, described in the next Section. 1. Matings giving no-white-eyed offspring all of one colour. Black, offspring all Black no-white in appearance, in agreement with theory. Number of young, Black no white. BN «BN 13 BNxRN 13 Red, offspring all Red no-whites in appearance, in agreement with theory. Red no-whites. RNxRN 61 RNxAN+R Livi Albino, offspring all Albino no-white in appearance, in agreement with theory. Albino no-whites (i.e. Colourless). ANxAN 489 346 E. J. ALLEN AND E. W. SEXTON. 2. Matings giving No-white offspring of 2 kinds in the proportion 3: 1. Number of young. Red no-whites. Albino no-whites. RN+AN x RN+AN Experiment 373 125 Theory 373 125 3. Matings giving No-white offspring of 2 kinds in the proportion 1: 1. Number of young. Black no-whites. Red no-whites. BN+RxRN Experiment 47 42 Theory At dt Red. Albino. RN-+AN xAN+R Experiment 14 10 Theory 12 12 4. Matings of normal-eyed animals carrying the factor for No-white, the offspring of crosses between normal-eyed and no-whites. (a) Those which give normal and no-white eyes of one colour in the proportion of 3 normal to 1 no-white, 1.e. 3: L. Black. Shee ee oe Black no-whites. B+NxB+N Experiment 24 i Theory 23 8 Red. Red, Red no-whites. R-+Nx R+N Experiment 440 149 Theory 44] 147 Albino. Albino, Albino no-whites. A-+R-+NxA+R--N Experiment 45 10 Theory 41 I4 A+NxA+N Experiment 246 72 Theory 238 (i) (b) Those which give normal and no-white eyes in two colours in the proportions 9:3:3: 1. Normal Red Normal Colourless R+A+NxR+A+4N Red. No-white. Albino. See Experiment 473 149 147 51 Theory 461 153 153 51 , Daal Tears > (BAR ENXBiR+N “Ra! yoni ag nel! APO Experiment 73 24 18 6 Theory 67 23 23 ie Note.—This is the K family VII, referred to on p. 326 in which the No-white mutation arose independently. | LOSS OF EYE-PIGMENT IN GAMMARUS. 347 (c) Those which give normal and no-white eyes in two colours in the proportions 3:1:3: 1. Normal Black Normal Red B+R+NxR+N Black. No-white. Red. No-white. Experiment = 45 1 24 10 Theory 31 10 31 10 B+R+AxR+N Experiment fh 3 3 | Theory 6 2 6 2 (d) Those which give normal and no-white eyes in three colours in the proportions 9:3 79:3: 6: 2. B+R+A+N Normal Black Normal Red Normal os x R+A+N Black. No-white. Red. No-white. Albino, (Albino No- white). Experiment 109 53 157 45 104 23 Theory 138 46 138 46 92 30) (ec) Those which give normal and no-white eyes in three colours in the Proportion: 21 s9):-923---12) = 4, B+R+A+Nx Normal Black Normal Red Normal _Colourless B-_R sey \ ZeNi Black. No-white. Red. No-white. Albino. ee &. Experiment 442 153 155 77 212 58 Theory 461 154 154 51 205 68 9. Matings of animals, one normal-eyed carrying no-white, the other no-white. (a) Those which give normal and no-white eyes in one colour in the proportion |: 1, Normal Black. Black No-white. B+NxBN+R Experiment 20s 12 Theory 16 16 Normal Red. Red No-white. R+NxRN Experiment 11 15 Theory 13 13 (b) Those which give normal and no-white eyes in two colours in the ‘proportions 3: 3:1: 1. Normal Black Normal] Red Black. No-white. Red. No-white, B+R+NxBN+R Experiment 26 21 3 10 Theory 22°5 22-5 75 Td 4 Section IV. By breeding together “albinos” and “ no-whites” a certain proportion of offspring are produced in which both the coloured retinal pigment and the white extra-retinal pigment are absent. The 348 E. J. ALLEN AND E. W. SEXTON. eyes of these are quite colourless. The figures for these are given under Section III, Summary (pp. 346 and 347, b, d and e). In addition to the colourless-eyed animals obtained by crossing albino- and no-whites, the colourless eye has arisen independently as a mutation. Colourless-eyed animals mated together give all colourless-eyed off- spring. The figures for these are given under Section III, Summary (p. 345. AN AN). GENERAL CONSIDERATIONS. The phenomena described in the present paper show a progressive degeneration of the eye of Gammarus, taking place in a series of definite steps or stages, each of considerable magnitude. In the end we see the entire loss of the eye-pigment, together with a broken and irregular arrangement of the ommatidia and a great reduction in their number. We only need to imagine the continuation of this process for a few further steps, and we should reach the complete absence of eyes found in those blind genera of Amphipoda, which live in subterranean waters. There is no direct proof that the change from the black eye-pigment of the wild animal to the red pigment, which occurred as a mutation in the eyes of the animals first used in the experiments, is due to the loss of a factor, but it seems not improbable that this may be the case. It is clear, at any rate, that these degenerative changes—the change from black pigment to red pigment, the entire loss of the coloured retinal pig- ment, the loss of the white extra-retinal pigment, and the degeneration in the form of the eye—all take place in exact conformity with Mendel’s Law. The only feature which may at first sight seem to show a diver- gence from this law is the more gradual process of degeneration of the white extra-retinal pigment, which gives rise to what we call the “ no- white ” eyes described in Section III. This, however, may perhaps be capable of explanation by supposing that the loss of the pigment takes place in a series of steps, instead of in one single step. The experiments recorded throw little or no light on the question of the conditions under which mutations arise or of the causes which give rise to mutations. The mutation of red eye-pigment has arisen once only in the whole course of the work and then after the animals had been kept under Laboratory conditions for only 2 generations. The complete loss of the inter-retinal coloured pigment, giving rise to the “ albino ” eye, was first seen in one brood belonging to a particular family as described on p. 275, the female parent being from stock which had been living under laboratory conditions for over 3 years, and the male parent also from stock which had been in the laboratory for several generations. Out of 733 offspring of the same family, 4 with albino eyes LOSS OF EYE-PIGMENT IN GAMMARUS. 349 occurred, all in one brood, two of which survived to produce offspring. All the animals used in the experiments were descendants of these two and the mutation has never occurred again. The loss of the white, extra-retinal pigment, on the other hand, has originated apparently independently on several occasions. It is dis- cussed in detail on p. 336. There seem to be some grounds for concluding that the loss of this pigment occurs when animals have been allowed to remain together for long periods and to interbreed promiscuously under somewhat unfavourable conditions as regards the quantity of water in which they are kept and the amount of food available. The loss of this pigment too, as already mentioned, seems sometimes to occur rather gradually and not suddenly as in the case of the change from black to red or the loss of the red. Quite colourless eyes have arisen independently from albinos by the loss of the white extra-retinal pigment, just in the same way that no- white eyes have arisen from normal red and black eyes. Cases of this kind have been discussed on pp. 336-338. A point of general interest which is somewhat strikingly illustrated by experiments described in this paper is the way in which the offspring of two abnormal, in this case degenerate, parents may themselves be quite normal in their characters, but are nevertheless capable of trans- mitting the abnormalities to their children. Such a case is that described on p. 333 (paragraph 2), where an Albino male (i.e. a male whose eye contained only the white extra-retinal pigment but neither black nor red inter-retinal pigment) was mated with a female Red No-white (i.e. one whose eyes contained only red inter-retinal pigment) with the result that all the young were black-eyed animals, normal in form and colour and indistinguishable on inspection from their wild ancestors (Plate VII, Figs. 4 and 5; Plate IV, Fig. 17). When, however, these or black-eyed animals of similar constitution are mated together the essential difference between them and the wild form comes out at once, all the abnormalities of the grandparents being reproduced in the grandchildren, and these abnormalities may even be combined in such a way that some of the grandchildren are more abnormal than the grandparents from whom they sprang. In the particular case mentioned the offspring consist, on the average, of 27 normal blacks, 9 black no- whites, 9 normal reds, 3 red no-whites, 12 normal albinos and 4 colour- less (albino no-whites). (Cf. Plate VI, Fig. 1.) Other results of a similar kind are recorded on p. 333 and the following pages. 350 E. J. ALLEN AND E. -W. SEXTON. EXPLANATION OF PLATES. Plate I. Fic. 1.—Explanation of the signs employed in the diagrams. Normal Black, i.e. with both the black retinal and the white extra-retinal pigments present. black no-white, with the black retinal pigment present, the white pigment absent. Red normal, with both the red retinal and the white extra-retinal pigments present. Red no-white, with the red retinal pigment present, the white pigment absent. Normal Albino, with the white pigment present, the coloured retinal pigment absent. Albino no-white or Colourless, with both the coloured retinal and the white extra- retinal pigments absent. A black spot attached outside the large circles indicates that the animal carries the factor for Black. Similarly, a red spot indicates that the factor for Red is carried, a small black circle the factor for Albino, and a small red circle the factor for No-white. The small V-shaped sign outside the large circles means that it has not been determined whether the factor usually indicated in the position where the sign is placed is present or absent. Fic. 2.—The matings of the Albino female A.C. (Albino carrying the factors for Black and Red) with a Red male and a Black male. Cross A. (p. 275) with the male R.2 from Pure Red Stock. One brood, I, and the young from their inter-matings. Cross B. (p. 278) with the male K.A. Black carrying the factor for Red from Family K (p. 326 and Plate V). Four broods, II, III, 1V and V. Many of the young died before reaching maturity. The constitution of those which survived to be tested is shown when known. Plate II. Cross C. The mating of the Albino female A.B. (Albino, carrying the factors for Black and Red), with the All-White male R.I.; the brood resulting from this mating is designated VI. Cross B. The mating of the Albino female A.C. (from the same brood and of the same constitution as A.B.) with the male K.A. from the family K, shown on Plate V, Fig. 1, Black carrying the factor for Red; the brood from this mating is designated IIT. The number of the offspring resulting from the cross-mating of Brood VI, with Brood II, together with the sex, and con- stitution when known, of the surviving animals, are shown below. Animals to which no letter is attached could not be tested for constitution. II.D 1, 2, 3, 4, are broods from the mating of two animals of Brood If. The number of young is shown, and the sex of those which reached maturity, but not the constitution, as, except in two or three instances, they were not tested for the factors carried. Plate III. Fic. 1.—Mating of Albino with Albino ; offspring all Albino-eyed. The male (h) and the female (1) are both from the second brood of II.D. (p. 279, Plate IT). Fic, 2.—Mating of Albino carrying the factor for Black with Pure Red ; offspring all Black-eyed. The male (A-}+ B) is from the first brood of IIT.B. (p. 279, Plate I); the female (R) is VI.B.2.¢. (p. 314, Plate II). Fie. Fie. Fie. Fic. Fic. Fic. Fie. Fic. Fie. Fic. LOSS OF EYE-PIGMENT IN GAMMARUS. 519)1 3.— Mating of Albino carrying the factor for Black with Red carrying the factor for Albino ; half the offspring Black-eyed, half Albino-eyed. The male (A-++ B) is from the same brood as the male of Fig. 2 (pp. 279 and 286), the female (R-+-A) IV.Z. (p. 285, Plate I). 4.— Mating of Albino carrying the factor for Red with Pure Red ; offspring all Red- eyed. The male (R)-and the female (A+R) are both from a brood of the female 1.G. of Cross A (p. 286). 5.— Mating of Albino carrying the factor for Red with Red carrying the factor for Albino ; half the offspring Red-eyed, and half Albino-eyed. Both the male (R-+ A) and the female (A+R) are from the same brood as the pair of Fig. 4 (p. 286). : +. 6.— Mating of Albino carrying the factors for Black and Red with Red No-white ; half the offspring, Black-eyed, carrying the factors for Red, Albino and No- white, and half Red-eyed, carrying the factors for Albino and No-white. The male (A+ B+-R) is II.D.1.j. on Plate II (p. 333); the female is a Red no-white from Family K (Plate V, Fig. 1). Some of this brood came to maturity, but died before their constitution could be proved ; their sex is shown in the diagram, but no distinctive letters have been given them. Plate IV. 1.—Mating of Black carrying the factors for Red and Albino with Pure Red ; halt the offspring Black-eyed, half Red-eyed. The female (B+ R-+ A) (also in Figs. 2 and 3) is VI.A.1.1L (p. 293, Plate II); the male (R) came from the Pure Red Stock. 2.— Mating of Black carrying the factors for Red and Albino with Black carrying the factor for Red only ; offspring in the proportion of 3 Black-eyed to 1 Red-eyed. Both animals from the one brood ; the same female (B+ R-+ A) as in Fig. 1 mated with the male (B+ R) VI.A.1.a. (p. 291, Plate I1). 3.—Mating of Black carrying the factors for Red and Albino with Red carrying the factor for Albino ; offspring should consist of Black-eyed, Red-eyed and Albino- eyed animals. The same female (B+ R-+ A) as in the two previous figures mated with the male (R+-A) VI.C.1.0. (p. 310, Plate I). 4.— Mating of Black carrying the factor for Red only with Pure Red ; half the offspring Black-eyed, and half Red-eyed. The same male (B+ R) asin Fig. 2, mated with a female (R) from the Pure Red Stock. 5.—Mating of Black carrying the factor for Red only with Black carrying the factors for Red and Albino ; offspring in the proportion of 3 Black-eyed to 1 Red- eyed. The same male (B+ R) as in Figs. 2 and 4, mated with the female (B+ R-+- A) VI.C.1.d. (p. 297, Plate IT). 6.—Mating of Black carrying the factors for Red and Albino with Red carrying the factor for Albino ; offspring should consist of Black-eyed, Red-eyed and Albino-eyed animals. 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