THE BNTER0PNEU8TA. 61 



EXPLANATION OF PLATES VII— XII. 

 Figs. 64—112, 



Illustrating Part II of Mr. Bateson's Paper on " The Mor- 

 phology of the Enteropneusta." 



Complete List of Reference Letters. 



a. Anus. al. Alimentary canal, at. Atrial cavity, be. ', ^ '. The anterior, 

 middle, and posterior body cavities respectively, bg. Rods bordering the gill- 

 slits, br. els. Border cells of proboscis gland (B. salmon eus). b. v. Blood- 

 vessel. C. N. S. Central nervous system {i.e. the cord of the collar region). 

 Cap. Capillaries of proboscis gland. Giro. Circular muscle-fibre. Cl.f. Collar 

 funnel. C. rg. Ring of nervous tissue round the collar. I), b. v. Dorsal 

 blood-vessel. D. mes. Dorsal mesentery. £). n. s. Dorsal nervous cord. 

 I), r. Cords connecting central nervous system with the skin. D. rdg. Dorsal 

 ridge of hypoblast in branchial region, dig. Digestive region of alimentary 

 canal. "E. Ectoderm, fl. Fold in vrall of collar funnels. g. s. Gill-slit. 

 g. s. S ^. First and second gill-slits respectively, g. sc. Lining of gill-sac. 

 a. sr. Supporting rods of gills, g. vs. Germinal vesicle, g. sp. Germinal spot. 

 gl. Proboscis gland, gl. s. Sac of proboscis gland, gnl. Granules in central 

 nervous system of B. salmons us. gr. Granules, probably excretory. 

 hi. Heart. int. Intestine. /. b. v. Lateral blood-vessel. I. rdg. Lateral 

 ridges separating the branchial chamber from the lower cavity of the gut in 

 the branchial region. I. msc. Longitudinal muscle-fibres. Lv. Liver, m. spz. 

 Spermatoblast cells. Mo. Mouth, msc. Muscle-fibres, mu. Mucous glands of 

 skin. mt^. Goblet cells of skin. mu". Long glands of collar skin of B 

 Kowalevskii. n. oil. Neural canal. Nch. Notochord. N. pr. Neural 

 pore. n. sh. Nervous sheath of proboscis. 0. Opening of collar pores. 

 Op. Operculum, ov.? Ingrowth of skin, probably an ovary, ov. Ovarian 

 follicle, ph. Pharyngeal region of gut with thick walls, per. Perforation 

 into liver saccule. pM. Fibrous substance of the nervous system. P. rg. 

 Ring of nervous tissue round proboscis, ph. c. Perihsemal body cavity. 

 Scl. Liver saccule. Sf. Surface of skin with anastomoses of ectoderm cells. 

 Sk. Skin. Skr. Sucker. S. r. Supporting rod of notochord. Sp. vlv. Spiral 

 fold in wall of gut in the digestive region. Si. Stripes occasionally seen in 

 preserved muscle-fibres. Stel. Stellate masses of cells in central nervous 

 system, t. pr. Tube of proboscis pore. ts. Testis. V. bd. Ventral band of 

 longitudinal muscle of B. Kowalevskii. F. A. ». Ventral blood-vessel. 



