384 MONTGOMERY. [Vol. XIII. 



The best fixative for the ganglion cells I have found to be cor- 

 rosive sublimate in alcoholic solution (50% alcohol); addition 

 of acetic acid to this solution is to be avoided. The best differ- 

 entiating double stain is Ehrlich's or Delafield's haematoxylin, 

 followed by eosin. The Ehrlich-Biondi stain does not furnish 

 as sharp differentiations as the preceding. For following the 

 course of the nerve tubules, preparations fixed for J^-i hour 

 in Hermann's fluid (platinum chl. -(- osmic acid -\- acetic acid) 

 may be especially recommended; Flemming's fluid (chromic -|- 

 osmic -j- acetic acid, in the stronger solution) is also valuable. 

 Osmic acid alone, as well as Kleinberg's fluid (picrosulphuric 

 acid), Lang's fluid, Perenyi's fluid (chromo-nitric acid), and all 

 single solutions of chromic acid are not to be recommended.^ 

 The gold-chloride method of Apathy ('91) might also be applied 

 with good effect to the nemerteans, though I have not had 

 opportunity to use it. 



II. Ganglion Cells. 



I follow Biirger's ('90b) precept in dividing these cells into: 

 (i) the smallest sensory cells; (2) the medium-sized cells; (3) the 

 large cells; and (4) the colossal neurochord cells (which are 

 absent in Lineus). The cells of these different categories may 

 be referred to respectively by the use of the roman numerals 

 I, II, III, IV. Burger's division of the ganglion cells I have 

 found to be a very natural one, being based upon morphological 

 differences as well as upon differences in regard to their relative 

 positions in the central organs. 



I can corroborate Biirger's ('90b, '9ib) conclusions that all 

 these cells are devoid of cell membranes, and that all are uni- 

 polar, — adopting his definition that a cell is unipolar when it 

 has but one pole from which the cell processes depart, whether 

 one or more processes are given off from the same pole. I have 

 found only one process of the cell, namely, the true nerve 

 tubule; and have never seen so-called "protoplasmic fibres" 

 such as he has figured ('90b, Fig. 61 g, h). Haller's ('89) con- 



1 For more detailed results upon the action of different fixatives and stains, cf. 

 Montgomery, '96b. 



