THE RADIATING ORGANS OF THE DEEP SEA FISHES. 181 



the pigment sheath (Plate 6, Fig. 30 c) is the connective-tissue membrane 

 mentioned above. The part of the capsule covering the cell mass outwardly 

 and separating it from the intermediate zone (Plate 6, Fig. 30 cr) is the 

 innermost of the two layers into which the connective-tissue membrane splits 

 up near the surface. From this outward part of the covering membrane 

 lying near the surface diverticles extend inwards dividing the outer two 

 thirds of the cell mass into somewhat irregularly pyramidal facets, the (distal) 

 bases of which are closed by the outer capsule membrane whilst the (proxi- 

 mal) apices are wide and open. The innermost part of the cell mass is not 

 thus divided into facets. The facets are occupied by large polyedrical cells 

 (Plate 6, Fig. 30 r) arranged in radial rows. Each cell contains a large and 

 conspicuous spherical nucleus ; its protoplasm is readily stainable with acid- 

 fuchsin. The same cells are met with on the inward side of the organ, but 

 here they form layers parallel to the surface of the organ and are not 

 arranged in radial rows. In the interior, a little below the centre, a mass 

 of much smaller cells (Plate 6, Fig. 30 m) is observed. These' look like 

 closely packed blood corpuscles. Possibly there exists here a blood sinus ; I 

 have not been able, however, to make out clearly a wall separating these 

 smaller internal cells from the larger ones around them. 



The intermediate zone (Plate 6, Fig. 30 t) has in sections the appearance 

 of a nearly empty space. It is in life perhaps occupied by a gelatinous sub- 

 stance with few slender cells. It may, however, be a mere artifact pro- 

 duced by shrinkage. 



The outer zone is composed of two layers, an inner layer of cylindrical 

 cells arranged vertically to the surface (Plate 6, Fig. 30 1) and an outer 

 layer of ordinary connective tissue composed of slender cells arranged para- 

 tangentially (cd) which forms the superficial covering of the organ in the 

 orifice of the pigment sheath. The protoplasm of the cylinder cells of the 

 inner layer is concentrated at their proximal ends which abut on the inter- 

 mediate zone. Here also the nucleus is situated. The rest of the cell body 

 is very transparent and the cell walls are difficult to make out. These cells 

 do not take stains readily and thus essentially differ from the polyedric cells 

 of the inner zone. In their microchemical behavior and their general ap- 

 pearance they resemble the cells of the middle region of the radiating organs 

 of Argyropelecus and Sternoptyx. 



A blood vessel, artery, (Plate 6, Fig. 30 b) of considerable size entering 

 the organ at the innermost point was observed in several sections. 



