ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 303 



bearing nematocjst batteries arranged in many rings, and fnrnisbed 

 with strong ranltiserial endoderm. During their fixed stage the polyps 

 are attached by an adherent base, connected to them by a narrow neck 

 and enclosed in perisarc. Multiplication by vegetative reproduction is 

 the rule, but there are also free medusoids. 



The polyps are minute, 0*15 to 1 mm. in height; the tentacles 

 are four to twelve in number. The living animals were colourless. 

 The tentacles and polyp-body are furnished with two types of nemato- 

 cysts (macrocnides and microcnides). The polyp is alternately fixed 

 and free, escaping from its basal bulb by rupture of the connecting 

 neck, and again developing a new basal bulb by a modification of its 

 proximal end. 



Reproduction is normally asexual, by means of buds set free in a 

 planula-like stage, by means of the detached basal bulb, and possibly 

 by means of longitudinal fission. The type of sexual phase is not 

 known with certainty. 



Hydroid Stage of Lar sabellarum.* — James F, Gemmill has found 

 this interesting hydroid at Tarbert, Loch Fyne. The material collected, 

 which included some small Sabellids, was brought to Glasgow and kept 

 under a "convection-current" circulation. Minute hydroid-like growths 

 were observed near the open ends of two of the Sabellid tubes, and 

 gonozoids were liberated, which were identified as the first stages of the 

 medusoid of Lar. The medusoid stages have been observed in the 

 Firth of Clyde plankton by Browne and Dick. The species, which was 

 described by Gosse, is of unusual interest, for the hydropolyp is strikingly 

 different from the usual gyninoblastic type, while the medusoid shows 

 characters to some extent intermediate between the Anthomedusse and 

 the Leptomedusaj. Gosse gave a very lively account of the quaint 

 mannikin-like individuals and of tbeir grotesque bending and swaying 

 antics round the mouth of the Sabellid tube. The most striking feature 

 of the genus Lar is the p )Ssession of only two tentacles springing from 

 one side of the base of a highly mobile bilabiate proboscis. The repro- 

 ductive individuals are slender and without tentacles, and bear the 

 gonozooids in clusters of three or four. 



Ecology of a Coral Reef.t — Alfred Goldsborough Mayer has made 

 an ecologual study of the fringing reef of Maer Island, the largest of 

 the Murray Islands in the Torres Straits. The reef flat is peculiar in 

 that the water is dammed by the Ijithothamnion ridge, which extends 

 in a narrow barrier along the seaward breaker- washed edge of the flat. 

 Thus at low tide the water over the reef flat becomes a marine basin 

 about two miles long, 1680 feet wide and only about eighteen inches 

 deep The water is impounded by the Lithothamnion ridge, and the 

 flat is never laid bare even by the lowest spring tides. About 3,600,000 

 living coral heads are found upon this submerged area. About forty 

 different species and twenty-two genera are represented, but 91 p.c. of 

 the living coral heads are referable to Porites (38 p.c), Seriato;pora 



* Glasgow Naturalist, vii. (1915) pp. 1-2. 

 t Proc. Nat. Acad. Sci., i. (1915) pp. 211-4. 



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