50 Proceedings of the Royal Society of Edinburgh. [Sess. 
Experiments with Crabs half-buried in Sand. 
When the animals were placed in the sand basin already described, 
most “dug themselves in.” The first procedure was to dig the thoracic 
legs into the sand and draw them up in a forward direction, at the same 
time elevating their bodies to an upright position, and then forcing them- 
selves downwards and backwards. In this way sand was removed upwards, 
both in front and behind. It was only when the anterior accumulation 
of sand became too high, and therefore liable to fall back into the excavated 
space, that the chelae were seen to sweep it aside. This process was con- 
tinued until the posterior accumulation had risen over about half the 
carapace. The animals then remained in the horizontal position with 
their legs buried, in a position semi-flexed inwards at the mero-carpal joints. 
The chelae, however, were fully flexed, the amount of flexion being limited 
by the carpal spines (Garstang (4)) ; the coxo-basal flexion, however, may 
be such that there is a large exostegal channel between the inner side of 
the propodite and the adjacent carapace, or none at all. 
The preceding experiments with ink were repeated. 
Exp. V. — When ink was injected near the prostomial opening the usual 
exhalent current was observed. When a sufficient channel existed between 
the chelae and the carapace a downward current was noticed, evidently 
going to the anterior ends of the sub-branchial clefts ; the ink could 
latterly be seen emerging in the prostomial stream. 
Exp. YI . — Injection over the sand-covered posterior end of the carapace 
also resulted in the reappearance of the ink in the prostomial stream. 
Occasionally reverse currents were set up, but of a longer duration than 
those previously seen. The ink was readily sucked in at the prostomium, 
and could be seen rising through the sand at the following points on both 
sides. Anteriorly, near the most lateral spine of the carapace, and 
posteriorly, in three “ eddies ” over the embedded postero-lateral border 
of the carapace — see fig. 1. When the current was again changed the ink 
was sucked in through these sand apertures. 
Frequently the exhalent (prostomial) current was directed to one side, 
and when reversion occurred, exhalent “sand eddies” were observed on the 
opposite side only, thus indicating that only one scaphognathite was working. 
Experiments with Crabs almost completely buried in Sand. 
Small crabs and sometimes larger animals will continue to bury them- 
selves until the whole carapace is covered with sand and there is only a 
triangular communication, by which the exhalent prostomial current 
