768 SCIENTIFIC RECORD FOR 1885. 



tion of the material collected by the Challenger Exi)edition. Another 

 is a systematic revision of the extinct American crinoids published in 

 the "Proceedings of the Academy of Natural Sciences of Philadelphia" 

 by Messrs. C. Wachsmuth and F. Springer. The concluding portion 

 of the latter will be published in 1886. A further notice of these and 

 other memoirs is therefore deferred. 



Asterioids. 



Nervous system of star- fishes. — In a memoir on the histology of Asterioids 

 Dr. O. Hamann has elucidated several interesting, and among them 

 is additional information respecting the nervous system. The well- 

 developed oral nerve-ring has long been known, but besides this there 

 is, according to Dr. Hamann, " a nerve-plexus in the oral disk ; this con- 

 sists of nerve-fibrils with scattered ganglionic cells, which pass into the 

 epithelial cells of the disk." In fact, an arrangement is manifested 

 "comparable" to one previously observed by Dr. Hamann himself in 

 the Holothurians. {Nachr. K. Gesellsch. Wiss., Gottingen, 1884, pp. 

 385, 386; J. B. M. S., (2), v. 5, pp. 652, 653.) 



Echinoids. 



Compound eyes in Ecliinoids. — In a Diadematid (probably Diadema 

 Setosum) occurring at Trincomalee, some peculiar characteristics have 

 been discovered by Drs. C. F. and P. B. Larasin. That sea-egg is cov- 

 ered with blue spots. One of these, when examined under the micro- 

 scope, shows on the surface "a mosaic" of polyhedya ("generally irreg- 

 ular hexahedra," but also peutahedra) which are so disj^osed as to call 

 to mind the compound eyes of insects or crustaceans. "Bach polyhe- 

 dron corresponds to a pyramid of very highly refractive substance, 

 the blunt edge of which is invested in pigment;" there "may be one 

 hundred or as many as one or two thousand pyramids in one spot; over 

 all of tbem the body-epithelium forms a thin ciliated layer, which may 

 be regarded as the cornea;" further, "each pyramid consists of a num- 

 ber of vesicular cells with quite hyaline contents, and in many of them 

 there is a distinct nucleus; this region may be regarded as that of the 

 lens and crystalline body." These organs are "directly placed on a 

 ganglionic i>lexus," and there is no distinct nerve intervening between 

 the two. When a hand is directed towards a point where these organs 

 are developed, the surrounding spines are seen to turn towards the 

 spot. It has been therefore inferred that the spots in question have the 

 junction of eyes capable at least of appreciating the difference between 

 "light and shade." {Zool. Anzeigerr. 8, pp. 715-720; J. B. M. 8., (2), v. 

 6, p. 253.) 



Holothurians. 



Values of differentiating characters. — The various parts and organs of 

 the Holothurians have been examined by Dr. K, Tjampert, in order to 



