HiCKSON — Notes on a Small Collection of Hi/drocorallinm. 499 



circular in section, but " the sides " can be distinguished from 

 the " surfaces " by the position of thebranchlets. The " surfaces " 

 are traversed by very fine longitudinal striations, and exhibit at 

 intervals rounded protuberances of a dark colour. These are 

 female gonads projecting on the surface from the subjacent 

 ccenosarc. The " sides " of the branch are marked by semicircles 

 or fragments of semicircles of cycle systems, indicating the former 

 position of complete cycle- systems that have become partially 

 imbedded in the growing coenosteum in the manner described by 

 Moseley.^ No cycle-systems or scattered pores of either kind, 

 dactylopores or gastropores can be seen on the surfaces of the 

 branch. The growing tips of the branchlets are entirely composed 

 of cycle-systems. Each cycle-system springs either from the right 

 side or the left side of the one immediately below it, that is the 

 system from which it has budded (PI. xix. fig. 5). In the older basal 

 parts of the branchlets the cycle systems are partially enveloped by 

 the growing coenosteum. Each cycle system is finely echinulate. 

 The styles are as Moseley described them. In the gastropore, 

 a small brush-like style standing up prominently from the base, 

 in the dactylopores a series of tooth-like projections standing out 

 vertically from the outer wall of the pore cavities (PL xx. figs. 1, 2). 

 The structure of the soft parts agrees very closely with the 

 description given by Moseley of the soft parts of S. densicaulis, 

 but I have usually found twelve tentacles on the gastrozooids 

 instead of eight. It is probable that this may be regarded as a 

 specific distinction between S. gracilis and S. densicaulis. 



Each dactylozooid consists of a short blunt teat-like process 

 directed almost at right angles to the direction of the pore towards 

 the centre of the system, and a long muscular slip firmly attached 

 to the teeth of the long serrated style (PI. xx. fig. 1). The 

 endoderm of the teat-like process is scalariform in appearance, 

 the ectoderm is thick and contains a number of very minute 

 nematocysts. I have not been able to discover any nematocysts 

 on any parts of the colony excepting at the tips of the dactylo- 

 zooids. 



The muscular slip of the dactylozooid consists of a thin 

 sheath of ectoderm covering a bundle of parallel muscular fibres 



iH. N. Moseley, "Challenger" Reports, volii. 



SCIEN. PEOC. ll.D.S., VOL. VII., PART V. 2 R 



