On the Anatomy of an Arenaceous Polyzoon. 11 



openings, and showing the differentiation into non- 

 digestive region above and digestive region below, 

 (o. g.) Opening from gizzard. (o. i.) Opening into 

 intestine, (ep.) The ccelomic epithelium, which invests 

 the entire alimentary canal, (c. e.) Columnar epithelium 

 of the upper, non-digestive portion of the stomach. 

 {cil.) Cilia of the columnar, nucleated cells. {s. c.) 

 Spherical cells containing yellow granules, forming the 

 wall of the lower, digestive portion of the stomach. 



Fig. 10. Optical longitudinal section through the wall of 

 an internode of Cryptozoon wilsoni. (chi.) Chitinous 

 wall, raised here and there into angular prominences — 

 (p.). {e.'p.) Deeply staining epithelium clothing the 

 inner surface of the tube. 



Fig. 11. A tubular zooecium of Cryptozoon ivilsoni, con- 

 taining a retracted polypide. The zooecium has been 

 separated by teasing, but portions of other zooecia are 

 still adherent on the right-hand side, and two sand 

 grains are still attached near the mouth of the zooecium. 

 (s. g.) Sand grains. (tv. z.) Wall of zooecium. {inv.) 

 Invaginated portion of zooecial wall, {riio.) Mouth of 

 zooecium. (w.) Retractor muscles ot invaginated 

 portion of wall of zooecium. (r. m.) Retractor muscle 

 of polypide. (a. m.) Attachment of retractor muscle to 

 wall of zooecium. (?■. p.) Rosette plates, indicating 

 where other zooecia have been attached. (ph.) 

 Phaiynx. (a?.) OEsophagus. C^'^'--) Gizzard. (st.) 

 Stomach. (int.) Intestine. (6. 6.) Brown body (1). 

 (fun.) Funiculus, {n. g.) Nerve ganglion. 



PLATE III. 



Fig. 12. A polypide of Cryptozoon wilsoni separated from 

 the zooecium b3^ teasing, and seen from the side as a 

 transparent object, (ten.) Tentacles. (ph) Pharynx. 

 (oe.) (Esophagus, (giz.) Gizzard, (st.) Stomach, (int.) 

 Intestine. (fun.) Funiculus. (a.) Anus, represented 

 open for the sake of clearness, though normally closed. 

 (n. g.) Nerve ganglion. (m. f.) Fibres of retractor 

 muscle. (71. m. f) Nuclei of muscle fibres. (t.) 

 Horny tooth of gizzard. (c. m. b.) Circular muscle of 

 gizzard seen in section. (n. e.) Nuclei of the ccelomic 

 epithelium investing the alimentary canal. 



