author's abstract of this paper issued 

 by the bibliographic service, july 12 



THE INTERMUSCULAR NERVE CELLS OF THE 

 EARTHWORM 



A. B. DAWSON 



Department of Anatomy, Loyola University School of Medicine 



SEVEN FIGURES 



INTRODUCTION 



The so-called intermuscular nerve-cells of the earthworm have 

 been referred to, usually incidentall}', in several papers on the 

 central and peripheral nervous systems of this animal, but in no 

 paper has a complete description of the size, form, distribution, 

 and relations of these cells been attempted. In view of the 

 more or less general acceptance of the annelid theory of the origin 

 of the vertebrates and since several annelids, viz., Sigalion, 

 Nereis and Allolobophora, have been pointed out as exemplifying 

 progressive stages in the transformation of the diffuse peripheral 

 nervous system of the lower invertebrates into the centralized 

 deep-lying system of the higher invertebrates and vertebrates 

 (Parker, '19, pp. 204-5), the writer has thought it worth while 

 to place on record the following observations, based upon a 

 study of a large amount of earthworm material which had been 

 prepared according to well-accredited neurological methods. 



In order to ehminate needless description and comment, both 

 in the review of literature and in the presentation of the results 

 of this investigation, it seems advisable at this time to outline 

 briefly some of the main features of the structure of the earth- 

 worm nervous system and to explain the descriptive terms which 

 will be used here. From each body somite three pairs of lateral 

 nerve trunks arise, one pair from the sides of the ventral nerve- 

 cord just behind the anterior septum and two pairs, more posterior 

 and close together, from the ganglionic mass itself. These lat- 

 eral nerve trunks pass ventrolaterally across the body cavity 



155 



