SEP 1 1900 



J 



ANATOMT AND CLASSIFICATION OF THE ABENICOLID^. 419 



The Anatomy and Classification of the Areni- 

 colidse, with some Observations on their Post- 

 larval Stages. 



By 



F. W. CJaiiible, ITI.Sc, 



and 

 J. H. AsliAVortli, D.Sc, 



Demonstraiors and Assistant Lecturers in Zoology, 

 Owens College, Manchester. 



With Plates 22—29. 



Contents. 



1. Introduction 



2. Distribution and Habits 



3. External Characters 



I. Segmentation 

 11. Prostomium 



III. Eyes and Nuchal Organ 



IV. Peristomium 

 V. Gills 



4. Setffi 



5. Epidermis . 

 0. Musculature 



7. General Anatomy of Internal Orgai 



8. Alimentary Canal . 



9. Vascular System : Heart-body 



10. Coelom 



11. Nervous System 



I. Brain 

 II. (Esophageal Connectives 



III. Ventral Nerve-cord 



IV. Giant-cells and Giant-fibres 



A. Giant-fibres 



B. Giant-cells 

 c. The Nature of Giant-cells and Giant-fibres 

 D The Occurrence of Giant-cells in Arenicola. 



VOL. 43, PART 3. — NEW SERIES. 



PAGE 

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