SARGASSUM. 



[ 676 ] 



SCALES. 



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

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



Fig. 624. 



Fig. 625. 



Sarcoscyphus Ehrharti. 



Fig. 624. Perichaete and perigone opened, showing the 

 young sporange emerging from the epigone. Magnified 

 25 diameters. 



Fig. 625. Perichsete and perigone opened, showing the 

 ba~<> of the seta surrounded by the epigone. Magnified 

 10 diameters. 



SARGAS'SUM, Ag. A genus of Fuca- 

 cese (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 conceptades, containing 

 spore-sacs and clusters of antheridia (see 

 FUCACE.E). 



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

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



SCALAR1FORM' VESSELS. See 

 SPIUAL STKUCTUKES. 



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. 22. 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 ante- 

 rior portion of the sac extends into or is 

 formed by the under portion of the cutis. 

 In these fishes also, the portion of the cutis 

 situated beneath the posterior projecting 

 portion of the scales contains a large num- 

 ber of very thin and minute crystals, to 

 which the silvery lustre of the skin is owing, 

 and which often exhibit 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 con- 

 fine 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 line fibres taking various direc- 

 tions, and best seen by scraping away the 

 upper portion of the scale after, maceration 

 in dilute acid (PL 22. fig. 11 a). The upper 

 portion consists of concentric plates, the 

 margins of which give rise to the concen- 

 tric lines so frequently seen in the scales 

 (PL 22. figs. 6, 10, 22, 23, &c.). These lines 

 correspond to the margins of the layers, and 

 often present a nodular or crenate appear- 

 ance (fig. 11 b) ; and towards the middle 

 of the scales they are frequently interrupted 

 and irregularly curved (tig. 11 c). The <ub- 

 stance of the upper portion appeal's 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 (PI. 22. fig. 12.) 



Many scales also exhibit radiating lines 

 (PI. 22. 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 

 (PI. 22. figs. 6 a & 7). At the posterior 

 portion of the same scales are often seen 



