Oct. 9, 1884] 



NA TURE 



5/ j 



considered requisite. It seems unlikely that the same herring 

 spawn twice a year, but that the fish which spawn in the spring 

 and autumn of one year do not spawn aga : n respectively till the 

 spring and autumn of the next year, in which case it is difficult to 

 account for two distinct races of herring. It may be supposed 

 that at first all herring were in the habit of spawning about the 

 same period, but as time went on they were found spawning 

 during every month of the year. Specimens of ova, for example, 

 have been sent nearly every week from the Aberdeenshire coast, 

 showing that herring have been spawning uninterruptedly in one 

 district for at least ten months, from August 1S83 to June 1884. 

 The explanation of why at the present day there are two great 

 spawning periods is not that spring and autumn are the two best 

 periods "for the depositing and hatching of the eggs, but that 

 these are the two most favourable periods for the appearance of 

 the fry, as then the surface-forms on which they feed are more 

 abundant, as examination of the Ballantrae Bank showed. In 

 the case of the herring the number of individuals does not depend 

 so much on the number of eggs hatched as on the number of fry 

 that survive. These when hatched are at first protected by their 

 minute size and great transparency, and, given sufficient food, 

 are likely to pass safely through the larval stage. If the larval 

 food were more abundant in autumn and in spring, more fry 

 would naturally survive at these periods, and this would ulti- 

 mately result in the formation of great shoals of autumn and 

 spring herrings. All that has been written on the migration of 

 the herring leaves us still very much in the dark as to either the 

 extent or the causes of it. Meantime, we may suppose that the 

 movements of the herring are regulated during a greater part of 

 the year by the supply of food, which naturally renders their move- 

 ments very inconstant, and during the rest of the year by what 

 may be termed their spawning instinct. This seems to imply 

 several things, but it specially leads the herring to select ground 

 suitable for the deposit of eggs, waters having a suitable depth, 

 and water which will provide abundant food for the young fry. 

 It has been long known, and was placed beyond doubt by the 

 Fishery Board investigations of 1862-63, that herring were wont 

 to spawn on hard ground. A very complete survey of the 

 Ballantrae not only corroborated this fact, but showed that the 

 herring even preferred to deposit their ova in the basin-shaped 

 gravel-coated areas, where presumably the water is stiller than 

 over the stone-covered ridges, and where it covered many square 

 yards with a layer nearly half an inch in thickness. Eggs were 

 also often found arranged in low masses over the surface of the 

 long stems of laminaria. In several instances the dredge had 

 apparently come upon part of the bank where the eggs 

 lay "to a very great depth," but on examination it was 

 found that the spawn, instead of forming thick masses, was 

 arranged in irregular heaps ranging from a quarter to half 

 an inch in thickness, and varying in size from scarcely an inch 

 to nearly six inches square. By laying the portions side by- 

 side in a tank it was possible to obtain a very accurate notion 

 of the arrangement of the undisturbed ova, which certainly 

 often form a regular layer covering several yards of the bottom. 

 On the east coast, judging from the specimens brought up by 

 the long-line fishermen, the herring seem to select hard ground 

 plentifully covered with sea firs, especially Hydrallmannia and 

 Antennularia. Fishermen and others believe that there is some 

 relation between the herring deserting any given spawning- 

 ground — such as the once much-frequented bank off Dunbar and 

 the equally famous Guillam Bank in the Moray Firth— and the 

 loss of herring-nets during storms, or when over-fished. The 

 reason is that nets loaded with putrefying fish, when left on the 

 ground, cause the herring to seek more agreeable banks else- 

 where. This pollution would be continued and extended by- 

 portions of the net continuing to fish during the whole season, 

 so that not only might the eggs first deposited be destroyed, but 

 fish which might have spawned on other portions of the bank be 

 taken, and their eggs, though shed, rendered useless. In this 

 way not only the greater part of a shoal, but, what is of even 

 greater importance, nearly all the eggs deposited during the 

 spawning period might be destroyed, and the survivors of the com- 

 paratively small brood hatched desert their birthplace as spawn- 

 ing-ground and cast in their lot gregariously with the first large 

 shoal they met with. In the artificial fertilisation and hatch- 

 ing of herring ova the natural process of spawning was followed 

 as far as possible, and many thousands of eggs treated in this 

 way on March 8 hatched out on March 28, 29, and 30, the 

 temperature varying from 41° to 44 F. When the eggs had 

 been plentifully supplied with pure water, the extremely active 



embryos kept revolving or wriggling inside the capsule, till this 

 ruptured and allowed the larval herring to escape head-foremost. 

 But if the supply of pure water had been limited, the capsule 

 gave way prematurely, the long, slender body escaped, but the 

 head remained within, and the embryo usually perished in spile 

 of all efforts to escape. The hatching was greatly expedited by 

 the temperature of the water being slightly raised. As soon as 

 the fry escape, they begin to try and ascend towards the surface, 

 which they generally succeed in reaching on the fourth day, 

 when they are found swimming freely about. This instinctive- 

 desire to rise to the surface as soon as they escape from the egg- 

 capsule is evidently intended to bring them to the vicinity of the 

 food, on which, after the fourth or fifth day, they depend for 

 nourishment. Sketches are given (Plates iv. v.) of herring, 

 illustrating the different positions of the fins. A map of the 

 Ballantrae spawning-bank (Plate vi.), and drawings of a colony 

 btUydralli,nannia falcata (Plate vii.) and Antennularia antennina 

 (Plate viii.). with cluster of eggs attached A series of figures 

 (Plate ix.) show the eggs deposited artificially on glass and natu- 

 rally on stones, gravel, and on a lost net dredged at Ballantrae. 



A number of interesting specimens received by the Board are 

 likewise described and figured.— (1) A new Blenny (Lumpenus 

 lamprefaformis, Plate x.), believed to be the first specimen re- 

 corded from the shores of the British Isles ; it measured 107 

 inches in length, and was taken in forty fathoms of water, fifteen 

 miles off St. Abb's Head. (2) A fine Torpedo nobitiana (Plate 

 xi.) taken off Lvbster in forty fathoms of water. (3) A Comber 

 [Scrannus cabr'illa, Plate xii.) taken off Shetland, the first re- 

 corded in the North Seas. (4) A Turbot [Rhombus maximus, 

 Plate xiii. ), dark on both sides, with an eye on each side of the 

 head and rounded frontal process, taken off Anstruther. (5) A 

 splendid Opah [Lamp-is /una), four feet in length, taken in 

 severity-five fathoms of water off Fluga, Shetland, and now being 

 examined by Prof. Tuner, F.R.S. Another item is a list com- 

 piled by Miss Maclagan of edible British fishes and mollusks, 

 with their Latin, French, Italian, and German synonyms. 



THE BRITISH ASSOCIATION 

 Section D — Biology 

 Department of Zoology and Botany 

 Remarks on the Characteristic Features of North American 

 Vegetation, by Prof. Asa Gray. — The first impression produced 

 on a visitor from Europe to the Atlantic coast would be the 

 similarity of the flora to that of England, many of the plants 

 being almost or quite the same. The larger number of these 

 are obviously introduced. The mullein, the toad-flax, the rib- 

 worts, the milfoil, the clovers, thrive by every roadside as in 

 England, and perhaps with even greater luxuriance, the compe- 

 tition being less. This strongly suggests the idea that the dis- 

 tribution of plants is not always due so much to adaptation as to 

 opportunity. As one proceeds westward and southward, the 

 difference becomes more marked, the European type gradually 

 disappearing. But as European settlements extend, the settlers 

 carry their plants with them, and the plants are well up to the 

 time, and travel by rail. On the other hand, some plants, but a 

 much smaller number, are carried from America to Europe, 

 and naturalised there. Such are Imfatitns fulva and Eriger on 

 canadensis. Turning from similarities to differences, one of the 

 first points that strikes a European visitor is the great wealth of 

 trees and shrubs. This Prof. Gray illustrated by giving the 

 number of European and North American species in the most 

 important arborescent orders. The reason of this is probably 

 to be found in the different conditions of the two continents 

 during the period of glaciation. The flora of Europe is 

 exceptionally poor in trees, and, on the return of a warmer 

 climate, the return northwards of those that survived in the 

 south was barred by the Mediterranean. The fossil remains 

 of trees belonging to many tropical orde-s are found in our 

 Miocene and Pliocene strata. In America, on the contrary, 

 there was nothing to prevent their gradual return from the south, 

 and accordingly we find solitary examples, or in some cases a 

 larger number of representatives, of many tropical riders among 

 the trees of the Northern States. Such ate Menisfermvm (Meni- 

 spermacece). Liriodendron (Magnoliacex), Diospyros [Ebenacex) , 

 Tecoma (Bignoniaceoc), and 'many others. This difference 

 is also promoted by the greater heat of the American 

 summer as compared with that of Europe. On the high 

 lands of North America are also many Arctic plants, which 



