164 



CARNEGIE INSTITUTION OF WASHINGTON. 



Lohophytum (Alcyonium) conferturn Dana, Sarcophytum glaucum Dana, and 

 Alcyonium flexile Dana. Lohophytum rigidum grows most abundantly over 

 the vertical reef edge, where it covers up and causes the death of the more 

 slowly growing stony corals, so that the increase in area of colonies of this 

 alcyonarian is an important factor in the ecology of the reef border, where 

 at present by far the most important coral-limestone formation is taking 

 place. In making the comparison of areas the perimeter of a colony at each 

 measurement was taken as the circumference of a circle and the resulting 

 areas were compared. In practice, in almost every instance the outline of 

 the base colony was by no means a true circle, so that the ratios given are 

 necessarily inexact. 



Lohophytum confertum, although most commonly found on the horizontal 

 reef surface, also frequently overgrows some of the stony corals upon which 

 it has found a place of attachment. Large continuous colonies of this species 

 are seldom found, because (as time goes on) the original mass becomes broken 

 up into an increasingly large number of small units. A relatively large barren 

 central area is commonly formed in old colonies and this barren area increases 

 with the age of the colony, which apparently Lives on for years in the form 

 of scattered small units. 



The increase in area of the two other species measured is a less important 

 factor, but individuals of either one of them may become the dominant 

 element on any protected reef area. 



The growth records for the four species mentioned above are briefly sum- 

 marized in the following table: 



Since the two first-mentioned species form at the base of the colony solid 

 spicule rock which becomes exposed as the soft tissues die and disintegrate 

 at this region, their linear measurements do not give a reliable indication of 

 the amount of limestone that they have secreted. In other forms, however, 

 from which the spicules are not released until the death of the colony, the 

 increase in size has a direct relation to the amount of spicules formed within 

 a given time. Specimens of which the weight as well as the dimensions were 

 recorded were planted on the reef at Pago Pago and at Suva Harbor (Fiji) 

 during the past summer. 



The alcyonarian fauna of Tutuila differs so greatly from that of the western 

 Atlantic that no comparison between growth-rates which could have any 

 value can be made on the basis of the data obtained in my studies in the two 

 regions. 



B. THE RESPIRATION RATES OF SOME SAMOAN ALCYONARIA. 



The respiration-rates of the four species of Alcyonaria mentioned above 

 do not conform to the order of activity of their growth. Alcyonium flexile 

 has the highest oxygen consumption at 82.8 c.c. O2 per kilogram of fresh 



