412 MONTGOMERY. [Vol. XIII. 



feinste, kaum messbare Fibrille verfolgen konnen, die in den 

 Ganglien einen verschiedenen Verlauf besitzt, in den Kom- 

 missuren von einer Gehirnhalfte zur anderen ihren Weg 

 nimmt und in den Seitenstammen entschieden langsgerich- 

 tet ist." 



. Now I have found that the nerve tubule, as far as it can 

 be followed, consists of a thin spongioplasmic sheath and an 

 enclosed, homogeneous, hyaloplasmic axis cylinder (Figs. 3, 36- 

 39). The axis cylinder is not a bundle of "primitive nerve 

 tubes," as held by Nansen, and as Biirger's ('90b) Fig. 56 

 would show. The assumption of the existence of the " primi- 

 tive nerve tubes " has probably had its origin in that those 

 spongioplasmic strands, which I have shown to be sometimes 

 prolonged for a short distance into the axis cylinder, had been 

 regarded by Nansen and his followers as the sheaths of such 

 primitive tubes; that such a structure is not present in the 

 nemertean axis cylinder I have already shown. My results would 

 show that the axis-cylinder process in its whole extent repre- 

 sents a single nerve tubule; and that a structural distinction into 

 a proximal " ganglion-cell process " and a distal " nerve fibril " 

 is not present. A "kaum messbare Fibrille," in the sense in 

 which Burger uses the term, namely, as a dense, deeply stain- 

 ing, non-tubular fibril, I have never found. And in fact, I 

 have found only a number of parallel nerve tubules at the 

 roots of the spinal nerves and in the first ventral commissure 

 of the brain, — points where Burger stated his "nerve fibrils" 

 to be most easily demonstrable. Therefore, Biirger, in those 

 studies ('90b) of his based upon stained sections, had either: 

 (i) supposed the true hyaloplasmic axis cylinder to be simply 

 an unstaining space between two " fibrils," and then had mis- 

 taken the sheaths of the axis cylinders for "fibrils"; or (2) 

 what, however, seems to be a less probable explanation, had 

 confused neuroglia fibrils with " nerve fibrils." But we must 

 conclude that in the fibrous core he had not seen the true axis 

 cylinders. This critique cannot be considered unjust, since 

 Burger had neglected to employ the two methods best qujifified 

 to demonstrate the axis cylinders in the fibrous core, namely, 

 Flemming's fluid and, better still, the fluid of Hermann. 



