1008 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



and proposes the name Semperia for those in which two tentacles are 

 smaller than the rest, and sucking feet are found in the interam- 

 bulacra as well as the ambulacra. 



Morphology of EcMnoids.* — Dr. W. Haacke thinks it is not yet 

 certain whether the " regular " sea-urchins are bilaterally or radially 

 symmetrical. The matter will probably be decided by the examina- 

 tion of as many abnormalities as possible, and with this end in view 

 Dr. Haacke has collected over 1000 examples of the Australian genus 

 Amhlypneustes. The questions to be answered are stated in full, but 

 until the answers are forthcoming it will be useless to state the 

 questions here. 



Larval Form of Dorocidaris papillata-f — In his study of the 

 development of this Echinoid M. H. Prouho sheds light on the 

 hitherto little known larval form of the Cidaridse. The ova, which 

 were laid in February, are of a whitish-yellow colour and slightly 

 transparent. The complete and regular segmentation results in an 

 ellipsoidal gastrula, with the blastopore at one flattened pole and a 

 group of very long cells at the other. The Pluteus form is perfected 

 three months after fertilization. The endoderm lining the alimentary 

 tract is ciliated throughout. Three different elements are distinguish- 

 able in the mesoderm : (1) colourless cells, with irregular prolonga- 

 tions ; (2) colourless globular cells, from which the spicules originate ; 

 (3) amoeboid mahogany-coloured cells, like those of the blood, pro- 

 bably originating from the ectoderm, where colour appears on the fifth 

 day. The ectodermic cells are large and flat, with polygonal contour. 

 Cilia are not abundant except on the long straight cells of the ciliated 

 band. 



The vaso-peritoneal vesicles originate as usual as two diverticula 

 from the enteric canal ; each divides at an early stage into two lobes, 

 one of which is applied to the oesophagus, while the other descends 

 along the stomach and intestine. The left vesicle is in communica- 

 tion with the exterior by the dorsal pore. The lining cells resemble 

 the colourless cells of the mesoderm. 



There are four pairs of arms — (1) posterior, (2) anterior, (3) an- 

 tero-lateral, (4) antero-internal. There are also independent cal- 

 careous structures, of which the most remarkable are the arched and 

 branched spicules supporting the " cupola," and in association with 

 contractile cross fibres. It is interesting also to note the presence of 

 an unpaired, median irregular spicule in the same position as the 

 unpaired arm of the Sj)atangoid larvae. 



There are no ciliated epaulettes, but the lobes along which the 

 ciliated band extends are very well developed. He distinguishes 

 (1) three lobes in the angle of the posterior arms, of which the 

 middle one is specially large ; (2) two pairs of dorso-lateral 

 lobes ; (3) one pair of lateral lobes between the posterior and 

 antero- lateral arms. These lobes, along with the reticulated spicules 

 and the much flattened cupola, give the larva a very characteristic 

 appearance. 



* Zool. Anzeig., viii. (1885) pp. 490-o. t Comptes Kcndus, ci. (1885) pp. 386-8. 



