DEPARTMENT OF MARINE BIOLOGY. 165 



weight per hour. Lohophytum confertum stands second in the hst, with an 

 oxygen consumption of 55.424 c.c. per kilogram per hour. Lohophytum 

 rigidum, although the first to succumb to increased temperature, stands third 

 in the order of rapidity of respii'ation, with an oxygen consumption of 42.40 

 c.c. per kilogi'am per hour. The remarkably low oxygen consumption of 

 21.30 c.c. per kilogram per hour shown by Sarcophijtum glaucum, when esti- 

 mated on the basis of its fresh weight, will be in part explained by the fact 

 that this species contains only about 6 per cent by weight of spicules. In 

 contrast to this low spicule content, both species of Lohophytum, however 

 carefully separated from their basal spicule rock, will contain nearly 20 per 

 cent of spicules, so that comparisons based upon the fresh weight of the 

 different species would of necessity cause the oxygen consumption of the 

 last-mentioned forms to appear much greater. 



Alcyonium flexile, which has the highest oxygen consumption, contains 

 only a slightly higher proportion of spicules than Sarcophytum, so that this 

 explanation is inadequate to satisfactorily account for the observed differ- 

 ences. As bearing upon this point, it may be mentioned that in my studies 

 on the respii'ation of some Alcyonaria at Tortugas, it was observed that those 

 species that have the greatest area in proportion to their weight have a far 

 more active respiration than do the less finely divided forms. When arranged 

 upon this basis, the Samoan species show a close agreement between the 

 area of surface for a given unit of weight and their rate of oxygen consumption. 



C. THE STRUCTURE OF THE FRINGING CORAL REEFS OF PAGO PAGO HARBOR. 



In order to determine the origin of the limestone making up the Samoan 

 coral reefs, the structure of the reef on the south side of the cove off the village 

 of Utelei, in Pago Pago Harbor, was studied in detail, first by making a deter- 

 mination of the character (origin) of the surface rock at intervals of 10 feet 

 along a line across the reef; secondly, by means of boring made with a Davis 

 calyx core-drill. 



When collecting the surface samples material was dug up in a number of 

 instances from a depth of 4 feet. At 83 of the 95 stations where examinations 

 of the surface material were made, some portion of the square yard of surface 

 over which samples were taken was found to be composed of rock of alcyo- 

 narian origin. Near the shore, where sand is abundant and very few living 

 organisms are to be found, "nodules" of L. confertum spicules were obtained 

 on digging to a depth of not more than 18 inches. On the lithothamnium 

 ridge, which was about 60 feet wide at this point, only one sam.ple of spicule 

 rock was found, and that at the base of a living colony of L. rigidum in the 

 breakers. At every station except one in the distance between the sandy 

 barren area near shore and the lithothamnium ridge some spicule rock was 

 found. Numerous areas barren of all living organisms were found surfaced 

 almost entirely with spicule rock. Observations at many other points on the 

 surface of this reef show that at least 75 per cent of its surface is, or has been 

 very recently, covered with Lohophytum for a period of sufficient length to 

 allow of the formation of spicule rock from a fraction of an inch to several 

 inches in thickness. 



At the northwest corner of this reef an area several acres in extent is thickly 

 carpeted with L. confertum, the continuous skeletons of which extend for 

 several feet below the surface of the reef. Dm'ing the long-continued growth 

 of these colonies the living tissue has died in many places, so that the skeletal 

 mass has become tree-like in form. Each of the branches of the skeleton is 

 at present crowned by a mass of living tissue, while at its base the skeletal 

 mass may be attached to the solid substratum by a single slender stalk. 



