in d. Naturgescb. d. uied. Thiere währ. d. Jahre 1876—1879. 725 



larity into Systems, in which a centrally-placed gastropore is sur- 

 rounded by a ring" of dactylopores. Nematocysts of two kinds present, 

 the one, the three-spined form , occurring only in Hydroids ; the 

 other ovoid in shape, with a thread beset witb a spiral of spines. 

 Gastrozooids short, cylindrical, with from four to six tentacles with 

 knob-like tips, set in a single whorl. Dactylozooids long, filiform, 

 and tapering, with an irregulär number of short knob-bearing ten- 

 tacles set on at irregulär intervals. Gonophores uraknown, but not 

 containet within special cavities in the substance of corallum (am- 

 puUae). 



Gen. MilleporaL. Genus with the characters of the family. 



Fam. Stylasteridae. Corallum arborescent, with a strong ten- 

 dency to assume a flabellar form and to the development of the 

 zooid pores on one face only of the flabellum or on the lateral 

 margius only of the branches composing it. In some genera a super- 

 ficial layer of the coral is living; in others nearly the entire mass 

 retains its vitality. Pores with tabulae in two genera also. The 

 gastropores usually provided with a conical calcareous protection 

 (style) at their bases. In some genera a rudimentary style present 

 only in the dactylopores. Pores scattered irregularly or grouped into 

 more or less symmetrica! Systems, composed of a centrally-placed 

 gastropore, surrounded by a circlet of dactylopores. In some genera 

 the mouths of the dactylopores appear as elongate Chambers, dis- 

 posed radially towards the centre of the gastropore, into which they 

 open, and the Chambers being separated from one another only by 

 their partitions (pseudosepta) ; the Systems (cyclo-systems) simulate 

 closely calicles of hexactinian corals. Nematocysts of two kinds, 

 large and small, and of uniform shape in all the genera. Three- 

 spined nemato-cysts absent. Gastrozooids cylindrical or flash-shaped 

 in form always entirely retracted within the gastropores when at 

 rest ; those of the former shape with four to twelve tentacles, set in 

 one whorl, and regulär in number in all the gastrozooids of each 

 species ; those of the latter devoid of tentacles. Dactylozooids simple 

 elongate-conical bodies, devoid of tentacles, sometimes capable of 

 entire retraction within the pores, sometimes not. Stocks of distinct 

 sexes. Gonophores adelocodonic, developed within sacs (gonangia) 

 which are contained within special cavities in the substance of the 

 corallum. Stocks of the two sexes alike in form as far as known, 

 except in the size of the ampullae, which are larger and more 

 prominent in the females. Ampullae containing in male Stocks 

 several goonophores ; in female , in some genera , a single gono- 

 phore, in others several. Spadix, in the female gonophores, cup- 

 shaped, embracing a single ovum only, which bekomes developed 

 into a planula within the gonangium. 



Archiv für Naüirg. XXXXV. Jahrg. 2. Bd. WW 



