10 Echino derma. 







are spherical bodies containing a number of pyriform sacs attached by threads to 

 their inner wall, and each enclosing a number of refractile spherules which stain 

 deeply. The wall of each sacculus is nucleated except on its outer edge which 

 projects somewhat from the surface of the body owing to the organ being swollen 

 by the mucus enveloping the pyriform sacs. The rudiments of the sacculi appeal- 

 about the 5 th day as 5 small groups of cells at the radial angles of the water- 

 vascular ring. Each group is hollow, with an epithelial lining, and from the flat- 

 tened side next the water-vessel certain cells are pushed out into the cavity of 

 the sacculus, but remain attached to its wall by fine processes. These cells deve- 

 lope into the pyriform spheruliferous sacs by modification of their protoplasm, 

 while the epithelial wall around them flattens out. They are not the zoospores of 

 symbiotic Algae as supposed by Vogt & Yung [see Bericht for 1886 Ech. p 6 ; 

 and 1887 Ech. p 5]. Neither are the yellow cells of the free swimming larva 

 invading amoeboid spores; for they appear before the rupture of the vitelline 

 membrane, and are not amoeboid, differing only in colour from the remaining 

 superficial cells of the larva. At the time of fixation the stem has 13-15 joints 

 which soon form complete rings from before backwards, closing in the radius C; 

 and longitudinal processes grow outwards from each side of the ring. The orals 

 and basals take up a transverse position, one of the former enclosing the water- 

 pore. The under-basals group themselves in a circle round the chambered organ, 

 just above the top stem-joint, with which they ultimately fuse to form the com- 

 pound centrodorsal plate. 



Hamann briefly describes the nervous system of Crinoids. Ganglion 

 cells, both bipolar and multipolar, are intercalated among the fibres of the am- 

 bulacral nerves which are not subepithelial but truly epithelial, retaining their 

 connection with the sensory cells, just as in Asterids. The radial nerves pass 

 directly downwards into the gut and form no oral ring. The mesodermic nervous 

 system consists of two parts, dorsal and ventral. The former is the envelope of 

 the chambered organ, with its radial extensions, which are solid and not hollow. 

 They contain delicate isolated fibrils with ganglion cells of varied types, some- 

 times arranged segmentally. Besides the nerves to the muscles and to the dorsal 

 epithelium, branches of the dorsal nerve trunks are given off between every two 

 muscle-groups to the ventral surface, where they join the second or ventral por- 

 tion of the mesodermic system. This consists of an oral pentagon on a level with 

 the water- vascular ring with nerves going from it to the tentacles and viscera. 

 This also gives rise to 5 pairs of nerves which lie at the sides of the water-vessels 

 and receive the ascending branches from the dorsal trunks. Phylogenetically it 

 is perhaps a part of the epithelial nervous system which has come to lie in the 

 connective tissue. In their nervous system as in their other characters the Cri- 

 noids must be regarded as the most highly developed Echinoderms. 



Carpenter's report on the Challenger Comatulae is mostly systematic, but con- 

 tains a few morphological details. The metamorphosis of the centrodorsal 

 in various species of Actinometra, which results in the formation of a stellate 

 plate devoid of any trace of cirri, is fully illustrated; and the modifications of 

 the basal star are shown in different species of Antedon and Actinometra . Two 

 specimens of the former and one of the latter genus are noted with 4 rays only, 

 and one of each genus with six. In all the tetraradiate individuals the missing 

 ray is the azygos anterior one. The Pentacrinoid larvae of 7 species are figured 

 and described, Antedon tenella, phalangium. multispina, tuberosa, and 3 undeter- 

 mined species. - - Several of the deep-water species of Antedon have wall-sided 

 arm bases, the outer parts of the rays and the lowest brachials being closely ap- 

 pressed and flattened laterally with sharp, straight edges. This character is 



