30 Coelenterata. 



The structures on the tentacles of Rhodarcea lagrencei, which Heicke con- 

 sidered to be taste organs, are probably nematocyst batteries. Beneath the 

 batteries of inc. there is a layer of ectoderm with numerous nuclei, probably 

 the site of formation of new nematocyst cells. The only difference between 

 the batteries of Actiniae and those of Madreporaria is that the former are com- 

 posed of thick-walled, and the latter of thin-walled, nematocysts. The stomo- 

 daeum contains numerous peculiar gland cells (Eiweifizellen - Schneider); 

 ciliated cells were not found. The muscle ridges on the septa are feebly 

 marked and sexual organs are wanting in the specimen examined. A list is 

 given of the Madreporaria hitherto recorded from the Antarctic, namely, 

 Gary. 2, Desmophyllum 2, Flab. 3, Leptopenus 1, Astrangia 1. All the species 

 are probably more or less circumpolar, but this is certainly the case for 

 (7. antarct.] all are inhabitants of the deeper littoral zone except Lept. discus 

 which occurs off the Crozets in 1600 fathoms. Those which are found also 

 in lower latitudes live there in deep water, and it is therefore striking that 

 bipolar species* are wanting, as the deep sea provides an opportunity of 

 passage from pole to pole. D. ingens, which occurs fossil in Sicily, is now 

 restricted to the Antarctic. - - See also Harrison & Poole I 1 , 2 ). 



Gravier( 5 ) states that in the bay of Tadjourah there are fringing reefs and 

 submerged coral patches, but barrier reefs and true atolls are not present. 

 Litkothamniv/m plays a smaller role here than in the reefs of the Pacific and 

 Indian Oceans. Several of the coral patches rest simply on sand, the corals 

 not being fixed to the substratum; these patches, situated some metres only 

 below the surface, are for the most part less than a kilometre in greatest length, 

 but their polyps are growing very luxuriantly. The author found 64 species 

 (6 n.) of Madreporaria at Tadjourah, of which 56 were collected on the Mara- 

 bout reef. 



Gravier( 6 ) records an example of Galaxea fascicularis, from Tadjourah, in a 

 dead area of which there are 3 young living calices, exactly covering old ones. 

 The polyps of the latter had evidently been dead some time, judging from the 

 erosion of the skeletal surface. The new calices have exactly the same 

 orientation as those on which they are placed; they can not have arisen from 

 3 larvae, but much more probably in each of the old calices there remained 

 living parts from which the new polyps have been formed. Possibly the layer 

 of living substance, sometimes seen exactly superposed over a dead coral, calyx 

 upon calyx, has arisen in this manner. In those by no means rare examples 

 in which layers are superposed and the lower part of the specimen is dead, 

 it is no more possible to fix the age of the living upper part than to estimate 

 the age of a rhizome which is constantly growing in front and dying away 

 behind. The author also describes, from the same reef, a Montipora monaste- 

 riata, fixed on a dead specimen of the same species and formed of several 

 parts which have arisen from living foci, at first separate and proliferating at 

 different times but finally uniting basally. This colony thus comprises several 

 groups, some juxtaposed, others superposed. 



Gravier( 7 ) gives examples of the struggle for existence observed in reef 

 corals at Tadjourah. On a specimen of Cyphastraa forskaliana grew a fine 

 colony of Hydrophorella contignatio ; one of the basal lobes of the H. had ex- 

 tended over the living part of the G. and had gradually destroyed it. The 

 free edge of the lobe of the H. was a little distance above the surface of the 

 (7., but the zone of the C. which was covered and deprived of food and light 

 was dead. A colony of Favia savignyi, fixed on the same specimen of (7., had 

 been partly killed by the //., which spread over one side of the F. and killed 



