652 SUMMARY OF CURRENT RESEARCHES RELATING TO 



or three weeks. The rate of growth depends largely upon the amount 

 of food ; in four months from the time of setting some bad grown to a 

 size of 2-2-| in. from mouth to tip of arm ; but others had not attained 

 tbat size in a year. With good opportunities a starfish becomes sexually 

 mature in less than a year. Regeneration of arms is frequent, but the 

 author did not find in the natural haunts any instance of the regeneration 

 of the disc, though this may occur in the aquarium. If a starfish be 

 torn apart and thrown overboard by the fisherman, it is unlikely that 

 the parts will survive and regenerate. 



Oral Skeleton of Ophiuroids.* — Prof. 0. zur Strassen agrees in a 

 general way with Ludwig's interpretation of the jaw apparatus — the 

 lateral mouth-shields and the bipartite mouth-corner pieces — but these 

 belong to the second and third segment, not to a first and second. The 

 halves of the vertebrae of the second (Ludwig's first) segment do not 

 form peristomial pieces — which are quite apart — but either degenerate 

 or remain as small rudiments in the corner of the mouth. The same is 

 true of the vertebral primordia of the true first or innermost segment. 

 But the important result of this sort of discussion, which is not very 

 easily followed, is that, if the author is right, the oral skeleton of 

 Ophiuroids is very different from that of Asteroids, in which the skeleton 

 comes from the two innermost segments, and the first ambulacralia are 

 often in a position similar to that of the peristomial plates in Ophiuroids. 

 In short, the supposed close relationship of Ophiuroids and Asteroids is 

 not supported by a detailed study of the mouth. 



Regeneration in Antedon rosacea. f — H. Przibram has made many 

 experiments as to regeneration and transplantation. The " disc ' : can 

 regenerate only in the direction of the anus ; it may be transplanted 

 with success to another animal ; the whole disc may be re-grown, or all 

 the arms ; a half can grow into a whole ; and so on. There seem to be 

 some limitations, however ; for regeneration does not occur if the central 

 nervous system be destroyed. 



Antarctic Holothurians.J — Edgard Herouard gives a preliminary 

 account of the Holothurians of the Belgian Antarctic Expedition. Their 

 chief interest is that they include Elasipodes taken from depths of only 

 410-460 metres, and also larvae of the same family. Among the new 

 forms is Rhipidothuria racovitzai g. et sp. n., the genus being intermediate 

 between Parelpidia and Scotoplancs ; Peniagorte vignoni sp. n. ; and some 

 other forms. Two larval Elasipodes were taken, one with four pairs of 

 ambulacral feet, and the other with three, both possessing a large ovoid 

 dorsal vesicle, which was pedunculated, and probably contained the 

 visceral mass. In all probability these larva? belonged to the sub-family 

 Elpidiineae, and the vesicle gives rise ultimately to the characteristic 

 dorsal veil of the members of that sub-family. 



Ccelentera. 



Scissiparity in Hydrozoa.§ — Armand Billard points out that this 

 occurs oftener than has been imagined. It has been observed by von 



* Zool. Anzeig., xxiv. (1901) pp. 609-20 (4 pis.). 



t Arch. Entwickmech., xi. (1901) pp. 321-45 (4 pis.). See Zool. Centralbl., viii 

 (1901) pp. 619-21. % Arch. Zool. Expe'r., is. (1901) pp. 39-48. 



§ Couiptes Kendus, cxxiiii. (1901) pp. 441-3. 



