No. 3.—The Anatomy and Histology of Caudina arenata Gould. 
By JohN Hiram GEROULD, 
CONTENTS: 
PAGE PAGE 
Introduction. so ae wail Pharynx . 147 
Methods 228 Stomach . 148 
2. Externalfeatures . . i126 Small intestine . 148 
3. Habitat, habits, food, etc. . . 128 Large intestine 148 
4. Anatomy and histology of the Cloaca 149 
ee e Mesenteries 149 
1. External epithelium . . . 129 2. Histology . . . 149 
2. Connective-tissue layer . . 181 a. Peritoneal epithelium ner 100 
Muscular cylinders . . . 132 b. Outer layer of connective 
3. Calcareous bodies . 183 tissue . 150 
Their development. . . 134 c. Muscle layer . 150 
Those of C. arenata var. d. Inner layer of connective 
AMAT ks v usc OO tissue. 152 
4, Musculature . 7. 185 e. Inner epithelium 152 
5. Inner epithelium . . . . 187 a. of the pharynx 152 
5. Nervous system . .197 B. of the stomach 153 
1. Central nervous system. . 138 y. of the small intestine . 153 
a. Circular nerve band . . 138 $. of the large intestine . 154 
b. Radial nerve bands . . 139 7. Respiratory trees . 154 
Outerband . . . . .140 8. Caleareous ring . 155 
Inner band . . . . . 141 9. Water-vascular system 157 
Sonnective-tissue parti- 1. Anatomy and histology . 157 
A an a. Circular canal . 158 
c. Neural canals 141 b. Stone canal and madre 
Hyponeural canals. . . 141 porite 159 
Epineural canals . . . 142 c. Polian vesicle 160 
Function of neural canals 143 d. Radial canals 161 
2. Peripheral nerves . . . . 144 e. Tentacles 162 
a. Nerves from nerve ring . 144 J. Posterior branches of the 
Tentaeular nerves . . . 144 radial canal. 164 
Buccopharyngeal nerves. 145 2. Contents of the water-vas- 
b. Nerves from radial bands 146 cular system 166 
6, Digestive system 147 3. Circulation of fluids in the 
1. General morphology . . . 147 tentacles utedo 
Mouth... 147 10. System of haemal leone . 168 
1Contributions from the Zodlogical Laboratory of the Museum of Comparative Zoölogy 
at Harvard College, under the direction of E, L. Mark, No. LVI. 
