The finer Structure of the Nerve Cells of Invertebrates. 15 



The question, however, concerning the presence in these cells of 

 chromophilous granules or in Pflücke's sense of "chromophile 

 Körperchen", which are in any sense homologous with structures found 

 in the nerve cells of Vertebrates, is, so far as known to the writer 

 a new one; and with the possible exception of Lugaro (whose paper 

 [20] I have not seen), was first suggested by PFLtJCKE when he said 

 on p. 514: "Uebereinstimmend mit den Befunden Nissl's und Anderer 

 an Ganglienzellen von Säugern können wir auch an denen des Krebses 

 die ganze Masse des Plasmas in zwei wesentlich durch ihr Verhalten zum 

 Farbstoff gekennzeichnete Substanzen scheiden, nämlich in eine stark 

 färbbare, structurgebende Substanz und in eine anscheinend homogene, 

 kaum oder überhaupt nicht gefärbte Zwischenmasse." 



At the present writing, although no classification of the nerve 

 cells of Invertebrates is attempted, it may be stated that the general 

 character of their chromophilous granules in many respects resembles 

 closely that of the "Körnchen" and "Körner" found in the nerve cells 

 of Vertebrates. That their mode of distribution in certain unipolar 

 cells, notably those of Helix, Arion, Astacus and Camharus, corre- 

 sponds closely to Nissl's "Fourth Type" (Gryochrome), in which fine 

 granules (Körnchen) are not regularly distributed in the cell body, 

 but are arranged in rows, or collected into small groups (Körner- 

 haufen). 



This paper deals exclusively with the finer anatomy of the nerve 

 cells of Helix and Arion, with special reference to the mode of 

 distribution of the chromophilous and fibrillar elements within these 

 cells. In addition to this, the question concerning the existence of 

 centrosomes and spheres in these cells will also be considered. Another 

 paper, now in preparation, will soon follow, dealing with the finer 

 anatomy of the nerve cells of Crustaceans and Vermes. 



These investigations were begun in the spring of 1895 in Pro- 

 fessor Flemming's laboratory at Kiel, whose hospitality, valuable 

 assistance and advise, I must gratefully acknowledge. My thanks are 

 also due to his Assistant Dr. Meves for the many favors received at 

 his hands; and to Messrs. J. S. Morgan and C. W, McAlpin of 

 New York, for their generosity in furnishing my laboratory at Prince- 

 ton , with all the necessary literature bearing on this subject. I also 

 wish to thank Professor Macloskie of Princeton for his kindness in 

 reviewing this manuscript. 



