56 Proceedings of the Royal Society of Edinburgh. [Sess. 
described, and although I do not agree with Claus, I think that it is 
possible that the flabella disperse the currents laterally so that they may 
bathe the entire length of the gills more thoroughly. In this manner each 
sub-branchial inlet will supply, not only the adjacent gills, but those anterior 
to it. For example, the fourth inlet supplies mainly the 9th gill, but to a 
lesser extent the 8th, 7th, and so on; while the first inlet supplies the 
anterior five gills, the 2nd, 4th, and 5th in particular, by means of the 
second inter-branchial gap. 
Summary. 
(a) The direction of the respiratory current is postero-anterior, whether 
the crab is above the sand or buried in it. 
(b) Reversal of this direction also occurs and is more frequent when 
the animal is buried or when a strong ink suspension is used during an 
experiment. 
(c) The sub-branchial cleft may be divided into four separate spaces 
which are in direct communication with gaps between certain gill origins, 
the whole constituting the sub-branchial inlets. 
(d) The direction of these inlets varies from postero-anterior to almost 
latero-medial. 
(e) They determine the direction of the inhaled currents within the 
branchial chambers. 
(/) The relation between the position of the gills and these inlets allows 
for a convenient and maximal flow. 
LITERATURE. 
(1) Bohn, “Respiration des Decapodes,” Bull, scient. France et Belgique , 1902, 
t. xxxvi, ser. 6, pp. 178-551. 
(2) Claus, “Neue Beitrage zur Morphologie der Crustaceen,” Arbeit. Zool. Instit. 
Wien , 1885, Bd. vi, Hft. 1, S. 1-108. 
(3) Garstang, “Habits and Respiratory Mechanism of Corystes cassivelaunus ,” 
Journ. Mar. Biol. Assoc ., 1896, vol. iv, N.S., pp. 223-232. 
(4) Garstang, “ Functions of Antero-Lateral Denticulations of the Carapace in 
Sand-burrowing Crabs,” op. cit., 1897, vol. iv, N.S., pp. 396-401. 
(5) Garstang, “ Respiratory Phenomena of Portumnus nasatus ,” op. cit., 1897, 
vol. iv, N.S., pp. 402-407. 
(6) Haan, de, “ Crustacem,” Siebold’s Fauna Japonica , 1850, p. 117. 
(7) Milne Edwards, H., “Recherches sur le mecanisme de la respiration chez 
les Crustaces,” Ann. Sci. Nat., 1839, t. ii, ser. 2, pp. 129-142. 
(8) Pearson, “Cancer,” Liverpool Marine Biological C., 1908, xvi, pp. 126-135. 
{Issued separately April 16, 1918.) 
