STUDIES IN THE EETINA. 313 



nuclear networks, any good microscope will show the con- 

 tinuity of these networks when, as in vei'y young eyes, tlie 

 nuclei are in contact or almost in contact with one another 

 (fig. 14). The short uniting threads which run from one 

 nucleus into the other are usually very numerous, — the union 

 between their networks being best seen by focussing up and 

 down rather rapidly. But the very short uniting threads in such 

 cases are not like the filaments shown in fig. 13; they are far 

 too thick, and they can only be regarded as filaments coated 

 over with other substances. The fundamental filaments 

 themselves are exquisitely delicate and achromatic. When- 

 ever, therefore, interuuclear bridges are seen with compara- 

 tive ease, what we see are not the fundamental filaments 

 themselves, but other staining substances coating them and 

 probably, as we shall see, streaming along* them. 



2. In retinas fixed with osmic vapour, the nuclei frequently 

 become blackened homogeneous bodies, having the appear- 

 ance shown in fig. 17 e. Most of them show one or more 

 exquisitely sharp points, frequently traceable into fila- 

 ments. Here and there, where the nuclei are close together, 

 unbroken filaments connecting them into groups may be 

 detected ; and others, which run, not to an adjacent nucleus, 

 but into the inner reticular layer, in order, as we shall see 

 later on, to join some nucleus of the innermost (''ganglionic") 

 nuclear layer, seem to be frequently preserved. I have noted 

 several times that the nuclear filaments that run into and 

 through the spongy reticuhir layer are less liiible to be 

 ruptured than those joining adjacent nuclei, unless the latter 

 are very close together. 



3. In specimens fixed with boiling corrosive sublinuite, the 

 fixative which first revealed the full length of the cones in 

 the amphibian retina (cf. Part I, this Journal, vol. xliii, 

 p. 23), the nuclei of the middle layer are, in some instances, 

 all balled together as small globules of refractive chromatin 

 with their connecting filaments ruptured; but in others they 

 have responded to the stimulus in the very opposite way, and 

 are changed into amoeboid masses with their radiating pro- 



