624 SUMMARY OF CURRENT RESEARCHES RELATING TO 



on, and the calcareous body thus formed appears to be enclosed in a 

 transparent wall, which has a spherical outline. Spines are very 

 early formed, and as in other Echinoderms are proportionately very 

 large, as compared with those of the adult. 



Organization of Star-fishes.* — Prof. E. Perrier discovered in tho 

 collections from Cape Horn a new incubating star-fish, to which he 

 gives the name of Asterias hyadesi ; the young were found to be 

 attached to the mother by a sort of lateral cord, which was inter- 

 radial in position, and was formed by a prolongation of the buccal 

 membrane. The youngest individuals were 2 mm. in diameter, and 

 on their disc there were three calcareous pieces ; M. Perrier thinks 

 that this shows the incorrectness of tho opinion of Messrs. Sladen and 

 Carpenter that the ten primitive pieces of young asterids remain on tho 

 disc. The " nervous layer " was found to be very poor in cells and to be 

 nothing but a supporting membrane traversed throughout its thick- 

 ness by a number of fibres ; these end in certain cells of the external 

 epithelium on the one hand, and on the other in the cells which have 

 been considered as forming the internal epithelial layer ; these colls 

 are multipolar ; towards the end of the arm they cease to form a 

 simple epithelial investment, and are supported by transverse trabecula? 

 which put them into relation with the cells of the sensory pits which 

 are ordinarily regarded as eyes. These then are the nerve-cells, 

 while the epithelial cells with which they are united across the 

 supporting layer, ordinarily regarded as the true nervous system, are 

 the sensory cells of the epithelium. 



On the wall of the sacciform canal which surrounds the hydro- 

 phoral tube there is attached a problematic organ which is prolonged 

 beyond the sacciform canal, in such a way as to form two organs 

 connected with the intestine, and giving off two lateral branches 

 which are in indirect relation with the genital glands. This proble- 

 matic organ, which has lately been called the chromatogenous organ 

 by Hamann, has in young Asterias hyadesi the form of a lateral 

 conical prolongation of the peritoneal membrane of the digestive sac, 

 and it contains a large number of vitelline bodies identical with those 

 of the wall of the sac. The lobes of its surface are continuous with 

 the trabecule which form tho living basis of the skeleton of the star- 

 fish, and it dilates at its external surface into membranes which 

 envelope the hydrophoral tube. This " collateral organ " of the tube 

 is then not a heart, but the site of the production of elements, some 

 of which, becoming free, form the corpuscles of the general cavity. 

 The canaliculi of the madreporite are due to nothing more than the 

 folding of the walls of the vibratile infundibulum, by which the 

 hydrophoral tube opens to the exterior ; M. Perrier is convinced that 

 the tube communicates, at the point where it unites with the apex of 

 the funnel, with the cavity of the sacciform canal. If the canaliculi 

 of the madreporic plate only lead into the hydrophoral tube, or its 

 upper expansion, the tube itself opens into the sacciform canal 

 laterally, and sea water can thus pass into the lacunar spaces which 



* Comptes Kendns, cii. (188G) pp. 1146-8. 



