TRANSACTIONS OF SECTION D. 773 



thickness is greater than that of the other layers of the integument, and in an 

 example ^^ in. long the deposit of silvery matter is so great as to form a layer 

 along the sides of the trunk live times the depth of the epidermis external to it. 

 In the species named the silvery matter is very precociouslj' developed, and the 

 presence of long spindle cells amongst its fibrous strands suggests that it may arise 

 from the lengthened cells of the deeper layer of the dermis. If not, then it is 

 merely a fibrillated condition of the mesodermic plasma, in ^vliich stray cells of the 

 dermis occur. This peculiar matter arises below and independent of the scales 

 ■which are formed as protrusions of the outer dermal layers. 



8. The Development of the Pharyngeal Teeth in the Labridce. 

 By Professor E". E. Prince. 



The wrasses are all characterised by the presence of toothed grinding plates in 

 the pharynx. Below the pharyngeal epithelium, which is six or seven cells deep, 

 the mucous layer cells form roimded dental sacs in which four distinct portions 

 can be distinguished at an early stage, viz. : (1) an enclosing laj-er of flattened 

 cells; (2) a single layer of nucleated round cells; (3) a columnaV layer of enor- 

 mous gland-cells, each with an eccentric nucleus, and secreting at the lower or 

 proximal end a clear homogeneous substance, similar to the osteoid matter, which 

 largely clothes the skeletal cartilages of post-larval Teleosteans ; (4) a papilliform 

 mass of rounded cells, representing the pulp-cavity of typical teetli. The last-named 

 layer secretes a granular substance which stains deeply, and constitutes an inner 

 cone of the developing tooth. This inner cone is soon covered with a clear coat 

 of osteoid matter, except at the acuminate tip, and the large gland-cells are active 

 in forming the clear non-staining matrix. The tooth lengthens, and by the time 

 that it pierces the pharyngeal epithelium it forms a lengthened conical structure 

 of clear matter, enclosing in its upper half an inner deep-staining cone which con- 

 tinues into the apex. AVheve the inner stained cone ceases a thickened stained 

 band occurs encircling the whole tooth. Compound teeth occur with two or more 

 pointed projections, and at their bases the teeth become attached below to the 

 nasi- and hypo-branchial cartilages and to the epibranchials above. The mucous 

 layer of the pharyngeal wall is crowded with dental sacs at various stages of 

 development. 



9. On the SUn of the Eedgehog. By E. W. Carliee, M.D., B.Sc, F.E.M.S., 

 S^c, Senior Assistant to the Professor of Physiology in the University of 

 Pjdiuhurglu 



Skin of Dorsal Surface. — "When the spines are clipped off, the skin is seen to 

 he of a dull leaden colour and very rugos^e ; the spines spring from depressions 

 between the rugosities. The skiu is very hrmly attached to the sub-dermal 

 structures. 



On section it is seen to consist of a thick layer of dense fibrous tissue thrown 

 into irregular elevations, over which a very thin epithelium is evenly arranged, 

 which also passes downwards to form the sheaths of the spines. Beneath the 

 fibrous tissue is a skin muscle of some thickness. There are neither sweat nor 

 sebaceous glands in connection with the spines, but often a great development of 

 adipose tissue beneath the muscle. 



The epithelium exhibits only two layers, a stratum corneum of little thickness, 

 and a rete Malpighi only two or three cells in vertical extent. The stratum 

 lucidum and stratum granulosum are both absent. The mucosa consists of thick 

 wavy bundles of connective tissue, with which are mingled near the epithelium 

 considerable numbers of pigment cells. There are few blood-vessels in this dense 

 tissue, but a free percolation of lymph. 



The panniculus carnosus consists of striped muscle of the usual type, and is 

 often of great thickness. 



The spine follicles are situated in the cutis vera, and are of large size. The 



