The oxygen in the water was determined by the Winkler method, using the precautions as regards the purity of reagents described by McClendon (1917b). Before taking the sample for analysis at the end of an experiment the respiration chamber was inverted several times to insure complete mixing of its contents. An extended series of comparisons showed that there was no detectable difference in the results obtained by drawing the water sample-250 c.c. through a glass siphon into the empty bottle or when siphoning into a bottle by the displacement of mercury (McClendon, 1. c.). The former, less complicated and much more rapid, method was therefore followed. The hydrogen-ion concentration of each fresh supply of water was determined by a colorimetric method and the amount of CO2 which it contained calculated from the P. and reserve alkali by a conversion table (McClendon, 1917a). In all the experiments it was found that so great a quantity of acid other than was being given off that the values obtained for a respiratory quotient were far higher than would be obtained from the combustion of pure carbohydrates. Since the respir atory quotients were in every instance greater than unity, whatever the duration of the experiment, theyhave not been included in the table.
The results of all the experiments are summarized in table 1, in which the figures in columns 2 and 3 are the averages obtained from 5 deter minations on specimens of various sizes of each species. Briareum asbestum has a central axis composed entirely of spicules, which in macerated specimens could not be certainly separated from those formerly contained in the co3nenchyma, so that both the skeletal masses are listed under the heading spicules.
Discussion.
The validity of Rubner's (1885) hypothesis that heat-production (oxidation) is in direct proportion to the surface area of an organism has been denied by Montuori (1913) for all aquatic animals on the basis of his experiments recorded in that paper. On the other hand,
Hoesslin (1888), Zuntz (1901), et a/., have maintained that their results on fishes support Rubner.
In Alcyonaria the surface in contact with the water varies greatly in different states of contraction or expansion of the colony. In the 12 species recorded in table 1 the surface area when expanded—all of them being able to completely retract their polyps—varied from 1.25 to 3.25 times that when the colony was in complete retraction. Since each species when undisturbed would arrive at complete expansion within a few moments after being put into the dark chamber, while on the other hand a slight agitation of the respiration chamber suf ficed to cause them to remain contracted, the comparison of the con sumption of oxygen under each of these conditions was a simple matter. While there were slight variations in the actual consumption of oxygen of any specimen in such a pair of experiments, the higher metabolism occurred as frequently when the specimen had all its polyps completely withdrawn as when they were in full expansion.
Although the area of tissue exposed to the water had no constant effect on the rate of respiration, there was a striking relationship between the proportion of surface to weight of the several species and the rapidity of their respiration. As shown in column 6 of table 1, those species which have the greatest surface for a unit of weight by far the highest metabolism. The areas used in these calculations were determined accurately for each specimen by measur ing the length and the diameter of each branch of a colony and treat ing them as cylinders or cones according to their shape. Under the conditions necessarily imposed while making the measurements, the colonies were always in a state of complete contraction, so that, when the specimens were in full expansion, the values of S/W would be from 1.25 to 3.25 times greater than those recorded in the table.