ANATOMY, HISTOLOGY, MORPHOLOGY, AND PHYLOGENY. JEck. 21 
was probably independently acquired in each group except Holothurians. 
Terminal tentacles (pp. 488-498). In Cucumaria the terminal tentacles 
resemble those of Urchins, and form a little circlet round the anal aper- 
ture (pi. xxvii, fig. 41). In Ilolothuria impatiens, on the contrary, there 
are no terminal tentacles. In Synaptids there are no radial water vessels, 
but the nerve ends in contact with the epidermis (pi. xvii, fig. 40). 
Otocysts of Synaptids and Elasipoda (pp. 498-500). Sphaeridia (pp. 501 — 
517). Nerve Terminations in the skin (pp. 507-512). In Synaptids the 
skin contains numerous papillae, composed of glandular cells arranged 
round a central group of filiform cells, in which a nerve terminates 
(pi. xxiv, fig. 5). Nerve Terminations in the Tentacles and Ambulacra 
(pp. 512-521). The sense-buds on the tentacles of Synapta are formed by 
an epithelial projection, at the tip of which is a small invagination of deli- 
cate cells bearing cilia (pi. xxvii, fig. 45). The papillae on the ambulacral 
tentacles of Antedon contain elongated fusiform bodies, of doubtful 
significance, which stain strongly with saffranin, but are not nuclei 
(pi. xxvii, fig. 44). Visual Organs (pp. 521-523). Water-Vascular 
System (pp. 523-549). In Synaptids (pp. 523 & 524) no trace of radial 
canals \cf. Ludwig (7) and Barth els infra]. Holothurians (pp. 524-*- 
529). Crinoids (pp. 529 & 530). Echinoids (pp. 530-536). Ophiurouls 
(pp. 536-540). Asteroids (pp. 540-542). Ambulacra and tentacles 
(pp. 542-549). Glandular appendages of the ambulacral ring (pp. 549- 
556). In Synaptids and Holothurians amibocytes are furnished by 
the Polian vesicle (pp. 549 & 550). In Crinoids , Spatangoids , and many 
Clypeastroids , the ambulacral ring has no glandular apparatus. In 
Dorocidaris papillata and Peronella orbicularis the ambulacral and 
lacunar rings are intimately connected, and the latter is glandular, and 
furnishes amibocytes to the water-vascular system by diapedesis. In 
Eckinodiscus biforis the lacunar ring, instead of being glandular allround, 
has a certain number of spongy masses placed in the interradii. The 
ambulacral ring sends diverticula into each of these masses. In Echinoids 
there is a well-defined spongy mass in each interradius, the so-called 
Polian vesicles, for which the name “vesicules spougieuses” is proposed. 
In Opliiuroids Polian vesicles reappear (pp. 553 & 554). In Asteroids there 
are Tiedemann’s bodies and Polian vesicles (pp. 554-556). Develop- 
ment and homology of the Madreporite (pp. 556-558) : the plates which 
are perforated by the water-pore are not homologous in different groups. 
Multiplication of Water Tubes and Madreporites (pp. 559-562) : in 
Asteroids and Opliiuroids a normal or abnormal increase in the radii 
usually corresponds with the presence of several stone canals. Species 
which multiply by division usually have several stone canals. Water- 
vascular System of Ophiactis virens (pp. 568-571). From the oral ring 
come off a number of canals in each interradius, which run towards the 
periphery of the disc and end coecally. They perhaps replace physiologi- 
cally the respiratory sacs, which are here wanting. Cavities of Irrigation 
(pp. 573-616) : these comprise (1) cavities of schizocoelic origin, in rela- 
tion with the nutrition of the nerve centres of the oral surface, present 
