768 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



Figs. 1296,1297. — Two views of cyst on nrni of Coinactinia mcridionalis containing ilyxostomum 

 cysticolum. 

 1298, 1299. — Two cysts on arm of Pachylometra inwqnalis containing Myzostomum tenuispi- 

 num. 

 1300. — Stalked cyst from dislj of Adelometra anr/ustiradia containing Myzostomum 



murrayi. 

 1301. — Cyst containing Myzostomum murrayi on specimen of Stiremetra J)rcvira(lia. 

 1302-1304. — Tliree views of cyst from arm of Pachylomctra inwqnalis containing Myzosto- 

 mum tenui^pinum ; fig. 1304 cyst broken open to show the female and the 

 dwarf male within. 

 1305. — Pinnule cyst not caused by myzostome from specimen of Antedon bifida from 

 Keumaes Bay. 

 1.306. — Egg-like contents of a pinnule cyst from specimen of Antedon bifida from 

 Cumbrae : the right side is drawn in surface view, left side in opticiil sec- 

 tion with cortical layer and the internal mass. 

 1307. — Pinnule cyst not caused by a myzostome from specimen of Antedon bifida from 



off Keumaes Bay. 

 1308. — Three deformities from specimen of an Antedon dredged by the Vettor Pisani 

 at Gibraltar ; a, groove-like deformity ; b, pinnule cyst ; and c, arm swelling. 



Plate 45. 



Fig. 1309. — Skeleton of central portion of a young Antedon bifida viewed dorsnlly with centro- 

 dorsal removed, showing central canal enlarged by absorption of part of original 

 basals. though nearer cavity of calyx, still contracted by secondary endogenous 

 growth; primary nerve stems and courses of their derivatives shown. (After 

 W. B. Carpenter.) 



ISlO.^Same, viewed ventrally, with radianal added. (After W. B. Carpenter.) 



1311.^ — Central portion of Leptometra celtica after removal of visceral mass. (After P. H. 

 Carpenter.) 



1312. — Arm of specimen of Antedon bifida in which the IBrj (axillary) is lacking, first bra- 

 chial of free undivided arm immediately following IBrj. (After W. B. Carpenter.) 



1313. — Dorsal view of skeleton of terminal portion of arm of mature pentacrinoid of Antedon 

 bifida. (After W. B. Carpenter.) 



1314. — Ventral view of same. (After W. B. Carpenter.) 



Plate 46. 



Via. 1315. — Section of gastrula of .intedon mediterranca early on the second day. (After Bui-y.) 

 1316. — Longitudinal vertical section of later gastrula (end of second day) of Antedon 



mediterranea, showing formation of me.soblast. (After Bury.) 

 1317. — Diagram of .structure of adult sacculus. (After Bury.) 



1318. — Pyriform sacs with refractive spherules from saccull at different ages, (.\fter Bury.) 

 1319. — Transverse sections of two pyriform sacs from saccull taken from adult specimens 



of Antedon mediterranea. (After Bury.) 

 1320. — Part of transverse section of eleventh day larva, showing development of sac- 

 culus. (.\fter Bury.) 

 1321. — Part of transverse section through same region about twentieth day. (After Bury.) 

 1322. — Arm pair of fully grovra pentacrinoid of Hathrometra sarsii, showing regenerating 

 arm. (After M. Sars.^ 



Plate 47. 



ViG. 1823. — Horizontal section of calyx and arm bases of Antedon bifida, flattened out, showing 

 axial canals. (After W. B. Carpenter.) 

 1324. — Central portion of Comatula pectivata after removal of visceral mass, (.\fter P. H. 

 Carpenter.) 



