424 MONTGOMERY. [Vol. XIII. 



bundles of the body wall.^ Thus in those frequent points in 

 the brain lobes and lateral chords where " strings " of the 

 inner neuroglia cells penetrate into the fibrous core, these 

 cellular ingrowths do not form compact masses, but their 

 individual cells are separated by irregular, unstaining spaces, 

 which branch out into the substance of the fibrous core. Often 

 such irregular, branching cavities are present beneath those 

 inner neuroglia cells which occur on the periphery of the 

 fibrous core (Fig. 37, Sp). The clefts or spaces produced by 

 these accumulations of body fluid may readily be distinguished 

 from cross-sectioned axis cylinders by their superior size, 

 irregular form, and absence of a limiting sheath. 



The results of Biirger's ('90b, '91b, '95) observations on the 

 finer structure of the fibrous core differ quite essentially from 

 my own. For he supposed its nervous elements to be dense, 

 staining "nerve fibrils," a view which my investigations would 

 show to be erroneous, and which has been sufficiently criticised 

 above. He consequently considered that the minute, unstain- 

 ing spaces of the fibrous core did not represent axis cylinders, 

 but clefts filled with body fluid, showing that he had overlooked 

 the true nerve tubules. Again, the nerve tube {mihi) of the 

 lateral chord, which he discovered and termed the "Faser- 

 strang," he stated to be composed of a bundle of deeply staining 

 " nerve fibrils," whereas I was able only on a few preparations 

 to find evidences of a structure in it, and then in the form of 

 a faintly staining reticulation (never "nerve fibrils"), which 

 probably represents the sheaths of enclosed nerve tubules. 

 Burger may have employed a fixing reagent which had caused 

 such an excessive coagulation of the contents of the nerve tube 

 as to have given the appearance of fibrils; but, as already 

 stated, I have never found any evidence whatever of the 



1 As a rule, the body fluid of the nemerteans can be considered to be a thin, 

 homogeneous, unstaining fluid, which fills the very numerous, usually minute, 

 clefts in the different tissues ; but I have shown ('97) that that portion of it 

 enclosed in the bundles of the longitudinal musculature, where it is found in great 

 quantity, becomes to a certain degree coagulated by corrosive sublimate, and then 

 presents a finely granular appearance. Before this observation was made, no one 

 had actually seen the body fluid, although previous investigators had assumed its 

 existence. 



