No. 3, — On some Points in the Anatomy and Histology of 

 Sipunculus nudus, L. By Henry B. Ward.^ 



Contents. 



Page 



I Introduction 143 



Methods 144 



II. External Anatomy .... 145 



1. Introvert 145 



2. Tentacular Fold .... 147 

 III. Histology 149 



1. Body Wall 149 



a. Cuticula and Hypodermis 149 



b. Cutis 150 



c. Pigment Cells .... 150 



d. Dermal Bodies .... 1-52 

 a. Bicellular Glands . . 152 

 p. Multicellular Glands . 155 

 7. Sense Papillse . . . 1-57 



e. Muscular Layers . . . 159 



2. Tentacular Fold . . 



a. Oral Wall .... 



b. Migratory Corpuscles 



c. Musculature . . . 



d. Vascular System . 



e. Aboral Wall . . . 



3. Nervous System . • 



a. Brain 



, a. Ganglionic Cells 



p. Internal Structure 



b. Cerebral Nerves 



c. Ventral Nerve Cord 



Plexi 



4. Cerebral Organ . . 

 IV. Conclusions 



and 



Bibliography 180 | Explanation of Figures 



Page 

 159 

 159 

 160 

 161 

 162 

 164 

 165 

 165 

 166 

 169 

 170 



171 

 172 

 176 



183 



I. Introduction. 



Some two years ago, while working on Sipunculus nudus in the zoo- 

 logical laboratory at Gottingen under Prof. E. Ehlers, my attention was 

 attracted by a peculiar organ in the region of the dorsal ganglion ; and 

 -Ithough it was a prominent feature of all transverse sections, no men- 

 tion of its presence was found in the literature on Sipunculus. The ob- 

 servations made at that time interested me so much that the opportunity 

 afforded by a short stay at the Naples Zoological Station last spring, 

 for which I am indebted to the great kindness of Prof. A. Weismann and 

 the Cultusministerium of Baden, was embraced to procure new, carefully 

 preserved material. A study of the literature on Sipunculus revealed 

 such lack of agreement between authors that a more general study 

 of the form seemed likely to yield results, and, on the advice of Prof. 



1 Contributions from the Zoological Laboratory of the Museum of Comparative 

 Zoology, under the direction of E. L. Mark, No. XXVL 



VOL. XXI. — NO. 3. 



