SINGLE CONES 



55 



occurs in a reticulum of many small granules. From the region of the 

 nucleus a short, thick, dendritic 'cone-foot' proceeds vitread to make a 

 synapse-like junction with a bipolar dendrite. 



& 



y/ 



Fig. 23— Rods. X 1000. 



a, generalized rod, showing organelles as they might appear if visible in the living cell; 

 note myeloidal spiral and centrosomic Fiirst fiber in outer segment, diplosome and Kolmer- 

 Held fiber proceeding therefrom in inner segment, b, rod of Protopterus cethiopicus— 

 unusual, in that it contains an oil-droplet, implying secondary origin from a cone (c/. Fig. 

 25). c, rod of goldfish, Carassius auratus; light-adapted (i.e., with myoid elongated — cf. 

 Figs. 62 and 63). d, common or 'red' (rhodopsin-containing) rod of leopard frog, Rana 

 pipiens; dark-adapted {i.e., with myoid contraaed — cj. Fig. 64). e, 'green' (Schwalbe's) 

 rod of Rana pipiens. i, rod of flying squirrel, Glaucomys v. volans; exemplifies the fila- 

 mentous type characteristic of many strongly nocturnal animals, g, human rod from near 

 the temporal side of the macula lutea. 



d, oil-droplet; e- ellipsoid; /- foot-piece; /- external limiting membrane; m- myoid (the 

 corresponding portion of the inner segment is non-contractile in e, f, and g); n- nucleus; 

 o- outer segment; p- paraboloid. 



