We have, in fact, no evidence on which to judge the question.  Perhaps it is least unreasonable to suppose that the idea of the rock-tomb was brought into the megalithic area by the same people who introduced the megalithic monuments, and did not result from contact with the Eastern Mediterranean.  Similarly we ought perhaps to disclaim any direct connection between the corridor-tombs of the megalithic area and the great tholoi of Crete and the Greek mainland.  At first sight there is a considerable similarity between them.  The Treasury of Atreus at Mycenae with its corbelled circular chamber and long rectangular corridor seems very little removed, except in size and finish, from the tombs of Gavr’ Inis and Lough Crew.  Yet there are vital points of difference.  The two last are tombs built partly with upright slabs on the surface of the ground, entered by horizontal corridors, and covered with mounds.  The Treasury of Atreus is simply an elaborated rock-tomb cut underground with a sloping shaft; as the ground consisted only of loose soil a coating of stone was a necessity, and hence the resemblance to a megalithic monument.

BIBLIOGRAPHY

OF THE MEGALITHIC MONUMENTS

GENERAL

Fergusson, Rude Stone Monuments in all Countries (London 1872). 
Bonstetten, Essai sur les dolmens (Geneva 1865). 
Mortillet, Compte rendu du congres d’archeologie
    prehistorique, Stockholm, 1874, pp. 267 ff. 
Reinach, Le mirage oriental, in L’Anthropologie, 1893, pp. 557 ff. 
Montelius, Orient und Europa. 
Borlase, The Dolmens of Ireland, Vols.  II and III. 
Reinach, Terminologie des monuments megalithiques
     in Revue archeologique, 3^{e} ser., XXII, 1893. 
Westropp, Prehistoric Phases (London 1872).

ENGLAND AND WALES

Fergusson, op. cit.
Recent Excavations at Stonehenge, Archaeologia, LVIII, pp. 37 ff. 
Flinders Petrie, Stonehenge:  Plans, Descriptions, and
     Theories (London 1880). 
Windle, Remains of the Prehistoric Age in England.
James, Sir Henry, Plans and Photos of Stonehenge and of Turnsuchan
     in the Island of Lewis (Southampton 1867). 
Evans, Sir A., Archaeological Review, II, 1889, pp. 313 ff. 
Lockyer, Sir N., Nature, November 21st, 1901. 
Hinks, XIXth Century, June, 1903, pp. 1002 ff. 
Lockyer, Sir N., Nature, LXXI, 1904-5, pp. 297 ff.,
     345 ff., 367 ff., 391 ff., 535 ff. 
Lewis, A. A., Stone Circles in Britain, Archaeological
     Journal, XLIX, pp. 136 ff. 
Thurnam, Ancient British Barrows, Archaeologia,
     XLII, pp. 161 ff., XLIII, pp. 285 ff. 
Lewis, A. A., Prehistoric Remains in Cornwall, Journal of the
     Anthrop.  Inst., XXV, 1895, and XXXV, 1905. 
Kermode and Herdman, Illustrated Notes on Manks
     Antiquities (Liverpool 1904).