+PLANS.+ The most radical change from the primitive basilican type was, as already explained in the last chapter, the continuation of the side aisles around the apse to form a _chevet_; and later, the addition of chapels between the external buttresses. Radiating chapels, usually semi-octagons or semi-decagons in plan, early appeared as additions to the _chevet_ (Fig. 122). These may have originated in the apsidal chapels of Romanesque churches in Auvergne and the South, as at Issoire, Clermont-Ferrand, Le Puy, and Toulouse. They generally superseded the transept-chapels of earlier churches, and added greatly to the beauty of the interior perspective, especially when the encircling aisles of the chevet were doubled. Notre Dame, as at first erected, had a double ambulatory, but no chapels. Bourges has only five very small semicircular chapels. Chartres (choir 1220) and Le Mans, as reconstructed about the same date, have double ambulatories and radial chapels. After 1220 the second ambulatory no longer appears. Noyon, Soissons, Reims, Amiens, Troyes, and Beauvais, Tours, Bayeux, and Coutances, Clermont, Limoges, and Narbonne all have the single ambulatory and radiating chevet-chapels. The Lady-chapel in the axis of the church was often made longer and more important than the other chapels, as at Amiens, Le Mans, Rouen, Bayeux, and Coutances. Chapels also flanked the choir in most of the cathedrals named above, and Notre Dame and Tours also have side chapels to the nave. The only cathedrals with complete double side aisles alike to nave, choir, and chevet, were Notre Dame and Bourges. It is somewhat singular that the German cathedral of Cologne is the only one in which all these various characteristic French features were united in one design (see Fig. 140). [Illustration: FIG. 122.--PLAN OF AMIENS CATHEDRAL.] Local considerations had full sway in France, in spite of the tendency toward unity of type. Thus Dol, Laon, and Poitiers have square eastward terminations; Châlons has no ambulatory; Bourges no transept. In Notre Dame the transept was almost suppressed. At Soissons one transept, at Noyon both, had semicircular ends. +Alby+, a late cathedral of brick, founded in 1280, but mostly built during the fourteenth century, has neither side aisles nor transepts, its wide nave being flanked by chapels separated by internal buttresses (Fig. 123). [Illustration: FIG. 123.--PLAN OF CATHEDRAL OF ALBY.]