ZOOLOGY. 595 



star fishes and Opliiuroids, aud "ro<,ailar witli polar diflerentiatioii " 

 in tlio Ediinoids. '' The various modes of cleavage arc of no value for the 

 phylogeiietrc history of the group; the intlueuee of cenogeuy is api)ar- 

 ent enough." For further and explanatory details the memoir of Pro- 

 fessor Selenka must be consulted, but his conclusions as to the genetic 

 relations of the group are of sutiicient general interest to warrant re- 

 l)e;rting here: " Evidence of the vennian origin of Kchinoderms is af- 

 forded by the primary mesoderm having the form of two primitive cells 

 and by the bilateial symmetry of the larval organs. The divisi«jti of the 

 archeuteric diverticulum into codomic sac and water-vessels corres}>ond 

 physiologically to that which the mesodermic sac undergoes in verte- 

 brates, aud to some extent in worms." {Selenlca^s Studien iiher Entwicke- 

 bdigsgeschichte, ii: J. R. ^^. S. (L5), iv, i»p. 573-574.) 



Crinoids. 



Reproductive function in Conmiula. — Interesting observations have re- 

 cently been made on the actions and apparent copulation of two indi- 

 viduals of the Cmnatuld meditieranea by Dr. C. F. Jickeli. The phe- 

 nomenon resembled that previously noticed in a star fish {Afiterina pib- 

 bosa) by Dr. H. Ludwig. The arms fell off as a climax, and this appeared 

 to con^tirm Studer's supi)ositiou that the loss of the arms, which often 

 occurs in star fishes, is connected with the discharge of the sexual i)ro- 

 ducts. {Zool. Anzeifjer, vii, pp. 444-449; Ann. (0 Mag. Xat. Ili.st. {6), 

 XIV, pp. 367-368; J. R. ^f. 8. (2), v, pp. 1(\-71.) 



Asterioids. 



A deep-sea siar-Ji.sh. — An interesting star-fish, obtained in Faeroe 

 Channel, at a depth of 555 fathoms, has been described by Mr. W. 

 Percy Sladen, under the name Miniasier Tizardi. Its interest arises from 

 the bonds of union with several quite diverse types, and it is indeed 

 what used to be called a synthetic or comprehensive type. It recalls 

 in different parts some Asteriida) (ISolaster)^ Astropectinidse, Goniaster- 

 idje, and AsterinidsB. It appears to be nearly related to a genus also 

 lately described, called Radiaster. {Tram. Koijal Soc. Edinb., xxx, pp. 

 579-584, I pi. ; J. Ii. M. 8. (2), iv p. 903.) 



Echinoids. 



Morphology of the Echinoids. — In connection with studies of the Echi- 

 noids, and especially of the deep-sea species constituting the fiimily 

 Pourtalesiidffi, Prof. S. Loven has considered the general characters of 

 the order. The skeleton is '• a hollow sac inclosing tlic visceral organs, 

 and constituted by three distinct systems — ambulacral, i)erisoniatic or 

 interradial. and calycinal or apical." On a careful study of this skeleton, 

 ir is found mat ''its constituent elements are in reality and fundamentally 

 arranged bilaterallv and svmnu'trically on either side of the mesial 



