7. Anthozoa (incl. Hydrocoralliaj. A. Zoantharia. 29 



tide falls and of expansion as it rises are in adaptation, in the first case, to 

 a medium with variable amount of oxygen (which is often small and con- 

 sequently there is danger of asphyxia), in the second case to a medium with 

 sensibly constant amount of oxygen. The closure of Actinia?, by bringing about 

 diminution of functional activity and less consumption of oxygen, augments 

 their capacity of resistance to asphyxia. 



Pieron( 3 ) states that Saga/rtia nivea, rosea and troglodytes, Actinoloba dianthus 

 and Tealia felina are less resistant to asphyxia than Actinia equina. When there 

 is a lack of oxygen in the water, specimens of fel, inflate the foot and take 

 up a position on the surface of the water, where they resist asphyxia while 

 others in the same vessel, but fixed, die. Those on the surface appear to 

 respire by the surface of the foot the integument of which is very thin. Under 

 the same conditions specimens of eq. may also release themselves and float 

 but more often they assume a position partly in and partly out of the water 

 in which their resistance is maximal and, according to the author's ex- 

 periments, they cease to use the oxygen in the water. "When kept in a sealed 

 vessel Actiniae invaginate their tentacles, contract their sphincter and secrete 

 an envelope of mucus in which condition they can resist asphyxia a long 

 time because of their diminished activity and small consumption of oxygen. 



Pieron( 5 ) concludes that Actiniae in a tidal pool react to the agitation of 

 the water and not to the variation in the amount of oxygen in it. In aquaria 

 they do not appear to react to variations of oxygen, and when they have lived 

 a long time in calm water, agitation of the water (which makes those living 

 in tidal pools expand) tends to cause them to protect their tentacles just as 

 if they were under the influence of mechanical shocks. - See Pieron( 2 , 4 , 6 - 10 ), 

 Bohn( 3 ) and infra, Mollusca p 4, Pieron( 2 ). 



Pax describes 6 pelagic Actinian larvae from Zanzibar. They are ovoid in 

 form, 1,1 mm. long and 0,8 mm. broad. A mouth is present, but no pedal disc 

 or tentacles, and the stomodseum, which is half as long as the body, has one 

 siphonoglyph. 26 complete septa, not arranged in pairs, connect the stomo- 

 dseum to the body wall, those in the region of the siphonoglyph are smaller 

 and perhaps last formed. The general ectoderm contains numerous nemato- 

 cysts but there are few in the stomodseuin; broad ectodermic nerve layer and 

 an ectodermal longitudinal musculature are present, the latter similar to that 

 met with only in the lower Protanthese. The mesogloea is homogeneous and 

 almost free from cells. Circular muscles are absent; there -are no longitudinal 

 muscles on the mesenteries and no parieto-basilar muscles. The endoderm is 

 very vacuolated and a glandular tract is indefinitely marked out on the edges 

 of the mesenteries just below the stomodseum. Zooxanthellse were not observed. 

 The blue colour of the animals in life, their ovoid shape and absence of 

 pedal disc and tentacles are correlated with their pelagic habitat; in these 

 respects they show convergence with the Minyadidae. These examples may be 

 regarded as larvae, which have been driven into the open sea, continuing to 

 grow but not attaining maturity. 



Thomson ( 2 ) describes a specimen of Parantipathes larix, trawled to the north 

 east of the Faeroe Islands, which measures 97 cm. in height. The previously 

 recorded range of this species is thus greatly extended. The diagnosis of the 

 species is slightly modified. 



Vaughan gives a detailed account of the corals of the Hawaiian Islands and 

 Laysan. The geographical and bathymetrical distribution of the Madreporaria 

 of this region are analysed. Most of the species are found in the shallow water 

 zone (0-25 fms.), 21 between 100 and 200 fms., 13 between 200 and 300 fms., 



