about to spawn the head is usually covered with small white tubercles; it is also at this time, as Buckland says, "the gentlemen wear green and red coats." Minnows are voracious feeders, and it is doubtful if their presence in trout-streams is beneficial when very numerous. No doubt they are food for the big fish, but do not they devour an enormous quantity of food of which the smaller trout ought to be the sole recipients? How well Keats describes their habits !— "O'er their pebbly beds, Where swarms of minnows show their little heads, Tempered with coolness. How they ever wrestle If you but scantily hold out your hand, That very instant not one will remain ; But turn your eye, and there they are again." The colour on the top of the head and back is darkisholive, mottled, and of a silvery-pink colour on the sides; the abdomen white, with a beautiful rosy or pink tint, varying in intensity; the irides and gill-covers silverywhite; dorsal fin pale-brown; pectoral, ventral, and anal fins much lighter in colour; the caudals light-brown, with one dark-brown spot at the base of the rays. Fin-rays dorsal, 9; pectoral, 16; ventral, 8; anal, 9; caudals 19. THE SHAD. The SHAD or TWAITE SHAD (Alosa finta), one of the Clupeidæ, is an anadromous fish, entering the fresh-waters about May and ascending the rivers for spawning purposes to a considerable distance. It was formerly abundant in the Thames, and one of its favourite haunts were the reaches between Putney Bridge and Hammersmith. There are very few, if any, to be found now in the Thames, but in the Severn they are more common, and generally follow the advent of the larger shad, Alosa communis, the Allice Shad. Buckland says the twaite is distinguished from the other native species by its having distinct teeth in both jaws, and by a row of rather large dusky spots along each side of the body; while in the allice shad there is only one spot, and that close to the side of the upper part of the gill-cover. THE TWAITE SHAD. The allice is a much larger fish, found in the Wye and Severn. Day says that the twaite shad is very capricious of taking a bait in the Severn, being occasionally hooked at almost any cast, at another time playing around the bait, but refusing to touch it. When hooked it affords some play. CHAPTER XIV. THE SALMONIDÆ. Dr. Günther ("Study of Fishes") places the Salmonida as the fifteenth family of the order PHYSOSTOMI. The first genus of this family comprise the Salmon, the Trout (Salmones), and the Char (Salvelinus); the latter being divided from the former by having no teeth on the body of the vomer, but only on the head of that bone. The British representatives of the first group are— The Salmon (Salmo salar). The Sea-Trout (Salmo trutta), with its varieties or The Sewin (S. cambricus). The White Trout (S. albus). The Fresh-Water Trout (Salmo fario), with its varieties or species, as The Loch Leven Trout (S. Levenensis). The Crass Puil Trout. The Estuary Trout (S. estuarius). The Orkney Trout (S. orcadensis). The Cornish Trout (S. cornubiensis). The Great Lake Trout (S. ferox). The Gillaroo Trout (S. stomachicus). The British representative of the second group, Salvelinus, is The Char (Salmo alpinus), with its varieties or species, as Torgoch (S. cambricus). Loch Killin Char (S. Killinensis). Gray's Char (S. grayii). Coles' Char (S. colei). The second genus, Thymallus, has only one British representative The Grayling (Thymallus vulgaris). The third genus, Coregonus, placed by some as the second, has three representatives— The Guyniad, Schelly, or Powan (Coregonus clu peoidis). The Vendace or Vendis (Coregonus vandesi). The Pollan (Coregonus pollan). The fourth genus, Osmerus, only one representative— The Smelt (Osmerus eperlanus). Much difference of opinion exists as to whether many of the British forms of the genus Salmo are to be considered as constituting species or varieties. The term species in natural history is employed to designate groups inferior to genera, but superior to varieties. Formerly, it was supposed the species were unchanging throughout the longest successions of generations, and would be defined as individual plants, animals, &c., agreeing in their appearance and composition, their similarity giving rise to the establishment of species; and individuals or species differing in circumstances arising from accident in plants or animals, from soil or climate, were termed varieties. About the end of the seventeenth century John Ray limited the term species in its natural history sense. His specific characters rested more especially on constant resemblance in outward form, but also on close resemblance of offspring to parent. At the same time he recognised variability. Linnæus's aphorism, " Tot sunt diversa, quot diversæ formæ ab initio sunt creata," notwithstanding Buffon's objection, was in a great measure recognised by Cuvier, and held in general acceptance until Darwin subverted it in 1859 on the publication of the "Origin of Species." Darwin maintained the variability of species, the variation continually taking place according to the external condition to which plants and animals are exposed. He thinks it difficult to distinguish varieties from species, and refers to the well-known changes which are produced by cultivation and domestication. He instances the selection man makes in order to produce new breeds and varieties, and considers that such selection often takes place in nature in the struggle for life which all plants and animals must undergo. Professor Huxley advocates the hypothesis which supposes the species living at any time to be the result of the gradual modification of pre-existing species. Day ("British and Irish Salmonida ") says: "We must have a permanence of variation from the original form to indicate a distinct species." He goes on to say, "that owing to too great importance having been given to inconstant variation, the number of species among this family has been unduly augmented, and varieties have been accorded specific rank, while every little variety of form, colour, or structure has also been reckoned as possibly demonstrating hybridity." The author of the article "Species," in the "Encyclopædia Britannica," says: "The rash generalisation, that distinct species are to be recognised by their incapacity for the production of fertile hybrids, has been overthrown, while closer study has cleared away the notion of the equal definitiveness of specific forms. "The want of any absolute standard of specific difference is largely made up by practical experience and common sense, and the evolutionary systematists are less in danger than were their predecessors of either exaggerating or understating the importance of mere varieties." The Salmonida are described by Dr. Günther as follows:-"Body generally covered with scales, head naked, barbels none. Margin of the upper jaw formed by the intermaxillaries mesially, and by the maxillaries laterally; belly rounded; a small adipose fin behind the dorsal; pyloric appendages generally numerous, rarely absent; airbladder large, simple; pseudo branchiæ present. The ova fall into the cavity of the abdomen before exclusion. Salmo.-Body covered with small scales; cleft of the mouth wide, the maxillary extending below or beyond the eye; dentition well developed; conical teeth in the jaw |