NOTE ON THE CILIATED PIT OF ASCIDIANS. 147 



EXPLANATION OF PLATES IX & X, 



Illustrating Lilian Sheldon's " Note on the Ciliated Pit of 

 Ascidians, and its Relation to the Nerve Ganglion and so- 

 called Hypophysial Gland ; and an Account of the Anatomy 

 of Cynthia rustica (?)." 



List of Reference Letters. 



A. Anus. A. Ep. Epithelium liniug atrial cavity. At. Atrial cavity. At. P. 

 Atrial pore. B. Communication between ciliated pit and ganglion, b. c 

 Blood-corpuscles, br. b. Branchial bar. br. s. Branchial slit. C. Canal of 

 ciliated pit. C. P. Ciliated pit. c. Constriction between the two kinds of 

 cells lining glands of stomach, c. c. Ciliated cells of endostyle. c. c. s. Ciliated 

 cells lining mouths of glands of stomach, c. m. Circular muscles, c. t. c. Con- 

 nective-tissue corpuscles. D. L. Dorsal lamina. D. Is. Duct of testis. E. 

 Blind end of ciliated pit. End. Endostyle. Ep. Epidermis. Ep. Int. Epi- 

 thelium lining intestine. Ep.ph. Epithelium lining pharynx. /./.Fibrous 

 coat of liver-cells. G. D. Common generative duct. Gl. Hypophysial gland. 

 g. c. Granular cells of pseudocoele. g. I. Granular contents of liver-cells. 

 H. Heart. Int. Intestine. Int. L. Part of intestine surrounded by liver-cells. 

 L. Liver-cells. /. Leucocytes. /. m. Longitudinal muscles, m. c. Mucous 

 cells of endostyle. M. ts. Muscles surrounding testis. N. G. Nerve ganglion. 

 0. Ova. CEs. Oesophagus. P. Communication of ciliated pit with mass of 

 tissue in Amarsecium. Pc. Pericardium. PA. Pharynx. Ps. Pseudocoele. 

 Ps.p. Processes of pseudocoele. p. c. Pigment-cells. R. Communication of 

 ciliated pit with (2). sp. Spermatozoa, st. Stomach. Sim. Stomodseum. 

 s.c.s. Secreting cells of stomach, sk.b. Skeletal rod. s.sk.b. Secondary 

 skeletal rod. T. Test. Ti. Mass of tissue lying ventral to ganglion in 

 Amarsecium. Is. Testis. (1) Anterior dorsal part of nervous system of 

 Amarsecium. (2) Posterior ventral part. (3) Nerve cord to tail. 



All the figures, except Figs. 12 and 4, were drawn with Zeiss's camera 

 lucida. The objective and ocular with which they are drawn are mentioned in 

 the description of each figure. 



Fig. 1. — Longitudinal section through the ciliated pit, ganglion, and gland 

 of Clavellina, showing the communication of the ciliated pit with the ganglion 

 and gland. (Oc. 2, obj. A.) 



Fig. 2. — Longitudinal section through the ciliated pit, ganglion, and gland 

 of an adult Amarsecium, showing the ciliated pit quite shut off from the 

 ganglion but communicating with the mass of tissue lung ventral to it. (Oc. 

 2, obj. D.) 



