746 William Patten 



the surface of the rod, where they unite with the snialler branches of the 

 external fibres. The axial fibres are continued through the end of the 

 rod, dividing into the two axial loops, /.«a-./. 'and l.ax.f:' One loopunites 

 two axial fibres , while the other extends along the external wall of the 

 rod. At X. is a clear vesicle, often present at that point. At the distai 

 ends of the rods the branclies of the external nerve fibres unite with each 

 other to forra the loops of the external nerve fibres. 



Fig. 21. A fragnient of the rete vitrosum of P. Jacobaeus, treated with hot chro- 

 mic acid, 55^ C. The hexagonal meshes forni a kind of crown for each 

 rod; at the coufluence of the bars thcre is a spikc, d, which project» a 

 short distance between the rods ; h is onc of the spikcs sceu from above ; 

 a is a portion of the network beneath the pseudo-retiuophorae. 



Fig. 22. A flake of rods from the retina of P. Jacobaeus, seen from their inner ends ; 

 treated with hot chromic acid for one half an hour, at 550 C. One sees tlie 

 two loops of the axial nerve fibres, and many sraaller fibrillae. Cam. 

 homog. ims. obj. 20. Leitz, oc. III. 



Fig. 23. Isolated lens from the eye of P. varius, treated for 24 hours in weak sul- 

 phuric acid; at«' and a-, one sees two specially well defined rows of cir- 

 cular fibres, and at s.L, the collectìon of fibres to forni the suspensory 

 ligamcnt. The lens is attached to the septal membrane by a uucleated 

 mass of fibres , l.l. and y. , many of which extend over the surface of the 

 lens, x; ät 1/ are radiating and circular fibres of the outer surface. 



Fig. 24. A cross section of a rod from the retina of P. Jacobaeus, showing the 

 axial nerve, the radiating and circular fibrillae of the retinidium and the 

 external nerve fibres. 



Fig. 25. Cross section through the distai ends of the retinophorae with their axial 

 fibres ax.f. and showing two for the inner ganglionic cells d.c.c. with 

 several nerve fibres on the surface for the retinophorae ; //. ' is one of the 

 very slender, fibre-like retinophorae often found in the retina of P. Ja- 

 cobaeus. 



Fig. 26. Cross section through the proximal ends of the roAs oi P. Jacobaeus , show- 

 ing the axial fibres with the radiating retiuidial fibrillae; at x, is a sec- 

 tion through the thin, structureless septum, scparating the retinophora 

 from its rod. 



Fig. 27. A median, cross section through the rods of P. Jacobaeus. 



Fig. 28. A stili deeper cross section , belonging to the same series as that of figs. 

 26 and 27, through the distai ends of the rods. At ex./, one sees sections 

 of the loops of the external nervo fibres. 



Fig. 29. Section through the outer layer of the argentea, showing the thin mem- 

 branes composed of minute, square plates with bevelled edges. 



Fig. 30. Surface vìew of a portion of a membrane composing the argentea. 



Fig. 31. An isolated, corneal celi of P. Jacobaeus with the median teeth 7n.t., and 

 the inner ones v.t., some of which are drawn out into fibres, x. 



Fig. 32. A portion of a retina of P. Jacobaeus, isolated entire and seen from the 

 under side; a — fh-epresent successive layers of cells seen by varyingthe 

 focus ; a, the inner layer for the retina ; the fibres, with their node-like 

 swellings on the periphery, representing the membrana circularis : the 

 nuclei, circularly arranged, He just beneath the circular membrane. At b, 

 are the swellings of the pseudo-retinophorae, fig. 38, n. rfP-, containing 

 a nucleus surrounded by a clear space ; at e, one sees the two sets of 



