470 Prof. Reid on the Voffmarus Islandicus. 



O' 



numerous small fibrous septa sent inwards from the inner surface 

 of the skin, and to the inner surface of the skin. Bundles of these 

 muscular fibres may be seen at some parts of the abdominal walls 

 running between the skin and aponeurotic lining of the abdomen 

 separated by numerous aponeurotic septa. Septa are also sent in- 

 wards from the inner surface of the skin to the interneural spines, 

 separating each pair of muscles which move the dorsal fin rays, 

 and numerous small septa are also at some places sent inwards 

 from the skin among the muscular bundles filling up the fibrous 

 sheaths. The strong central partition, and the fibrous prolon- 

 gations inwards of the skin impart an amount of strength to the 

 whole body, and afford an extent of firm attachments to the 

 muscular bundles, which the imperfectly developed neuro-skele- 

 ton could not of itself have supplied. Of the three uppermost 

 muscular sheaths, the lower one, immediately behind the occiput, 

 is very much wider than the other two. Opposite the ninth ver- 

 tebra they were nearly equal in width and measured each about 

 Y^^ths of an inch, but on proceeding backwards the upper and 

 lower diminished in width much more rapidly than the middle, 

 so that opposite the thirty- sixth vertebra while the middle mea- 

 sured x^ths of an inch in width, the lower measured only y%ths 

 and the upper y^ths of an inch. The upper muscular sheath 

 lies over the upper extremities of the spinous processes of the 

 vertebrse, and the portion of the lower extremities of the inter- 

 neural spines and of the muscles of the dorsal fin rays interposed 

 betwecQ these. Of the two undermost muscular sheaths, or those 

 placed below the lateral line of the body, the one next the spine 

 is much narrower than the lower. 



The microscopic examination of the tissues of this animal fur- 

 nished some interesting results. 



Skin. — The skin is thin, being about ^^^th of an inch in thick- 

 ness, is in close contact with the subjacent muscular bundles, 

 and is destitute of scales. It may be divided into two parts — an 

 epidermic portion and the chorion or true skin. The more ex- 

 ternal of these, or the epidermic portion, may also be subdivided 

 into two parts. One of these is composed of thin, narrow and 

 elongated fibres (fig. 2), upon the presence of which the bright 

 silver colour of the skin depends. These fibres are arranged in 

 bundles, are firmly agglutinated together, those of the same 

 bundle run parallel or nearly so to each other, and have one of 

 their flat surfaces looking outwards, and the other towards the 

 subjacent layer of the skin. A layer of similar fibres covers the 

 anterior surface of the iris, giving it a bright silvery colour. It is 

 very difficult to separate these fibres from each other, and in 

 attempting this they were generally broken into fragments of 

 greater or less size. Those of the iris were not so firmly agglu- 



