ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 55 



stolons ; they are quite retractile ; the tentacles are turned inwards in 

 the retraction ; there is no horny cuticle in the basal part of the polyp. 

 Miiller recognizes R. rosea and R. catenata. 



Formation of Axis of Corallium.* — Robert Miiller finds that Coral- 

 lium possesses an axial epithelium of ectodermic origin which agrees with 

 that of the Gorgonids. The axial skeleton is formed by the excretion of 

 crystalline calcareous bodies, whereby a cementing of the mesodermic 

 spicules is brought about. The union of the latter with the axial skeleton 

 is due to divergence of the adjacent cells of the axial epithelium, which 

 afterwards come together again. 



Plexaurids of 'Siboga' Expedition^ — C. 0. Nutting reports on the 

 Plexaurids collected (1899-1900) by the 'Siboga' in the Dutch East 

 Indies. Five new species of Plexaura and three of Euphxaura are 

 described. A Ceylonese form, Plexaura antipatkes vsLT.flexnosa Thom- 

 son and Henderson, is included (May l'.UO) in a new species, P. aggregate, 

 but in February 1910 Thomson and Russell raised it to specific rank as 

 Euplexaura fiexuosa. This will require to be looked into. A new genus, 

 HicJcsonella, is established and thus defined : — " Plexauridae with a thick 

 ccenenchyma, calices included and on all sides of the branches, horny 

 axis cylinder, and two very different types of spicules — very small, short 

 warty spicules, and long slender bar-like smooth spindles." The name 

 of Simpson's new genus, HicJcsonella, more recently established for a 

 Gorgonellid type, will have to be changed. 



Isidae of ' Siboga ' Expedition. :£ — C. C. Nutting describes Isis reticu- 

 lata sp. n. which goes beside /. Jiippiris, hitherto the only representative 

 of the genus. It differs from I. Jvippuris "in manner of branching, 

 reticulation, slenderness of twigs, colour, and most of all in the character 

 of the spicules." The author describes a new species of Ceratoisis, two 

 of Acanella, two of Mopsea, and two of a new genus, Peltastisis, which 

 " bridges the narrow gulf between the Isidse and Primnoidse, in that it 

 combines the jointed axis of the former and the characteristic operculum 

 of the latter, which it also resembles closely in its spiculation." 



Gorgonidse of 'Siboga' Expedition. § — C. C. Nutting describes 

 LopJiogorgia pinnata sp. n., Leptogorgia formosa sp. n., Stenogorgia miniata 

 (Val.), S. studeri sp. n., and Platyeaulm sibogee sp. n. 



Gorgonellids of ' Siboga ' Expedition.||— C. C. Nutting describes two 

 new species of Gorgonella, one of Verrucella, one of Juncella, one of 

 Scirpearella, two of Nicella, and erects two new genera, Plumigorgia and 

 Isidoides, He has not had the advantage of utilizing J. J. Simpson's recent 

 revision of the Juucellids, and thns retains a genus like Ctenocella, which 

 seems bound to be merged with some other. The genus Sdrpearia is 

 ruled out, since Scirpearea was originally used for a Pennatulid. The 

 new genus Plumigorgia has symmetrically arranged, delicate, pinnate, 



* M.T. Zool. Stat. Neapel, xx. (1910) pp 101-7 (4 figs.) 



t Monographie xiiiB. ' Siboga ' Expeditie, 1910, pp. 1-20 (4 pis.). 



J Tom. cit., pp. 1-24 (6 pis.). § Op. cit , No. 7, 10 pp. (3 pis.). 



|| Op. cit., No. 6, pp. 1-39 (11 pis.). 



