SARGASSUM. 



[ 562 ] 



SCALES. 



pi. 7. fig. 56, and pi. 13. fig. 113; Endlicher, 

 Gen. Plant. Supp. i. nos. 474-1. 



Fig. 629. 



Fig. 630. 



Sarcoscyphus Ehrarti. 



Fig. 629. Perichaete and perigone opened, showing the 

 young sporange emerging from the epigone. Magnified 

 25 diameters. 



Fig. 630. Perichaete and perigone opened, showing the 

 base of the seta surrounded by the epigone. Magnified 

 10 diameters. 



SARGASSUM, Ag. A genus of Fucaceac 

 (Fucoid Algae), gulf-weeds, known from the 

 allied sea-weeds by its stalked globular air- 

 vessels. The receptacles are small, linear 

 and mostly clustered at the base of branches, 

 and pierced by numerous pores leading to 

 conceptacles containing spore-sacs and clus- 

 ters of antheridia (see FUCACE^E). 



BIBL. Harvey, Brit. Mar. Alg. p. 14. 

 pi. 1 A ; Greville, Alg. Brit. pi. 1. 



SCALES, OF FISHES. These bodies 

 were formerly regarded as epidermic forma- 

 tions, analogous to the nails, &c. of the 

 higher animals, which later observations have 

 shown not to be the case. 



Each scale is contained in a distinct sac of 

 the skin or cutis, covered externally with its 

 pigment layer and epidermis. The cutis 

 itself consists of interlacing fibres of areolar 

 tissue with formative cells. The pigment 

 layer is composed of elegant pigment-cells 

 with long processes. Immediately above the 

 upper surface of the scales lies a very fine 

 membrane, distinct from the cutis, in which 

 the impressions of the irregularities of surface 

 existing upon the scales are visible. 



In some fishes, as the eel, the scales do 

 not project beyond the surface; hence the 

 eel is commonly supposed to possess no 

 scales. They are easily seen, however, in a 

 dried piece of the skin, mounted in balsam, 

 covered by the skin with its pigment- cells 

 (PI. 17. fig. 19), the whole forming a very 

 beautiful object. 



In many of the common cycloid fishes, as 



the roach, dace, &c., the scales project pos- 

 teriorly from the surface, carrying before 

 them the thinner and closely applied outer 

 layer of the cutaneous sac, whilst the anterior 

 portion of the sac extends into or is formed 

 by the under portion of the cutis. fn these 

 fishes also, the portion of the cutis situated 

 beneath the posterior projecting portion of 

 the scales, contains a large number of very 

 thin and minute crystals, to which the silvery 

 lustre of the skin is owing, and which often ex- 

 hibit very beautifully the colours of thin plates . 

 The signification of the various parts of 

 structure of the scales has not been satis- 

 factorily determined ; hence we must confine 

 our remarks to simply pointing out the 

 structural peculiarities. 



Most scales consist of two portions, an 

 under, composed of numerous layers made 

 up of very fine fibres taking various direc- 

 tions, and best seen by scraping away the 

 upper portion of the scale after maceration 

 in dilute acid (PI. 17- fig. 11 a). The upper 

 portion consists of concentric plates, the 

 margins of which give rise to the concentric 

 lines so frequently seen in the scales (PL 17. 

 figs. 6, 10, 22, 23, &c.). These lines cor- 

 respond to the margins of the layers, and 

 often present a nodular or crenate appearance 

 (PL 17. fig. 116); and towards the middle 

 of the scales they are frequently interrupted 

 and irregularly curved (PL 1 7. fig. 1 1 c). The 

 substance of the upper portion appears to 

 be structureless. 



In a transverse section, the projecting 

 margins of the laminae belonging to the 

 upper portion of the scale, are seen as so 

 many teeth (PL 17. fig. 12). 



Many scales also exhibit radiating lines 

 (PL 17. fig. 23), corresponding to furrows in 

 the upper portion of the scales ; these are 

 sometimes closed above so as to form tubes, 

 and have been regarded as nutritive canals. 

 Near the centre of some scales, as those 

 of the perch, are numerous rounded corpus- 

 cles or solid bodies, imbedded in the sub- 

 stance of the upper portion of the scales 

 (PL 17. figs. 6 a & 7). At the posterior 

 portion of the same scales, are often seen 

 spine-like processes (PL 17. figs. 6b & 9), 

 with rounded or angular bodies resembling 

 the last in appearance arranged in rows at 

 their bases (PL 17- fig. 8). 



The scales of the eel appear to be princi- 

 pally composed of similar bodies, differing 

 only in form, and arranged in concentric 

 rows (PL 17. figs. 20 & 20 a). They are 

 solid, impregnated throughout with calca- 



