STUDIES ON NERVE CELLS. 



I. THE MOLLUSCAN NERVE CELL, TOGETHER WITH SUM- 

 MARIES OF RECENT LITERATURE ON THE CYTOLOGY OF 

 INVERTEBRATE NERVE CELLS. 



W. M. SMALLWOOD AND CHARLES G. ROGERS. ^ 



With Plate I and Thirteen Figures in the Text. 



I. Introduction 45 



II. Morphology of the Gasteropod Nervous System 48 



III. Lymph Canals 50 



rV. Vacuoles 55 



V. The Nissl Bodies. 61 



VI. Pigment 69 



VII. The Centroso.me in Nerve Cells 73 



SuMM.\RV 75 



Liter.'vture ; 76 



I. INTRODUCTION. 



The purpose of this paper is twofold: First, to summarize and 

 correlate the more important contributions on the structure of 

 invertebrate nerve cells exclusive of the neuro-fibrillae (a special 

 problem which cannot be adequately treated in the space allotted 

 to this review); and, second, to present our own studies on the 

 structure of the gasteropod nerve cell with special reference to 

 the problem of the so-called Nissl bodies, whose nature is still in 

 controversy. It has been maintained that these bodies are arte- 

 facts. Inasmuch as we have been able to cause them to appear 

 by feeding experiments and have been able to photograph them 

 in the living and unstained nerve cells, we feel reasonably sure of 

 their actual existence and shall make suggestions as to the manner 

 of their development, as well as their probable function. In a 



' Contributions from the Zoological Laboratory, Syracuse University, C. W. Hargitt, Director. 



