DISTRIBUTION OF SUBCUTANEOUS VESSELS IN GANOIDS IO3 



have a somewhat rectangular arrangement. Certain twigs tra- 

 verse the superficial layer of the filament, opposite to and parallel 

 with the spaces separating the septa, and these are connected by 

 transverse branches. This coarse network cannot be confused 

 with the very fine respiratory network (Fig. i8, jRes.IV.) ; for the 

 latter is more profundus, being confined to planes or septa, 

 which are at right angles to the so-called lymphatic network. 

 With a magnification of 450 diameters (Fig. i8rt) the meshes of 

 the respiratory network are not as large as the meshes of the 

 lymphatic network as viewed with a magnification of 50 diame- 

 ters (Fig. 19) ; hence the caliber of the respiratory capillaries is 

 almost infinitesimal when compared to the lymphatics. After 

 leaving the area of the respiratory septa, which is toward the 

 outer edge of the filament, the lymphatic network assumes a 

 somewhat different character; here, as is shown in the lower 

 part of Fig. 19, the meshes become crowded closer together ; 

 while on the outer edge of the filament, in the region of the 

 efferent filament artery, the meshes become elongated in the 

 direction of the artery, which is exactly at right angles to their 

 greatest length in crossing the filament. An examination of 

 the basal portion of the filaments and the membranes overlying 

 the efferent branchial artery with a lens (Fig. 17), or better still 

 a microscopic preparation of this region (Fig. 20), discloses the 

 fact that the lymphatic network of the branchial filaments are 

 continuous with a similar network found on the outer and inner 

 surfaces of the branchial arch (Figs. 17 and 20, Br.A.L.JV.). 

 Branchial Arch Lymphatics {Nutrient Veins P). — One of 

 these vessels (Fig. 17, Br.A.L.T.) runs along the inner surface 

 of each arch, near its inner margin. It receives numerous 

 radiating branches, which collect an extremely rich network 

 (Fig. 17, Br, A. L.N.) that lies in the deeper membranes and 

 connective tissue lining the arch, and which is distinctly lym- 

 phatic in the character of its meshes. This trunk also receives 

 large accessory branches that gather a similar network from the 

 other or outer side of the arch. So fine is this network that its 

 meshes cannot be seen without the aid of a lens. At various 

 intervals delicate branches could be traced to the outer mem- 

 brane, where they collect an extremely minute capillary net- 



