MS. B. 30.  The principal development is thrown on the diagonal axes by square chapels with three niches; on the principal axes are inner recesses communicating with outer ones.

The plan Pl.  XCIII No. 2 (MS. B. 22) differs from this only in so far as the outer semicircles have become circular chapels, projecting from the external square as apses; one of them serves as the entrance by a semicircular portico.

The elevation is drawn on the left side of the plan.

MS. B. 19.  A further development of MS. B. 18, by employing for the four principal chapels the type Pl.  LXXXVIII No. 3, as we have already seen in Pl.  XCI No. 2; the exterior presents two varieties.

a) The outer contour follows the inner. [Footnote 2:  These chapels are here sketched in two different sizes; it is the smaller type which is thus formed.]

b) It is semicircular.

Pl.  LXXXVII No. 2 (MS. B. 18b) Elevation to the first variation MS. B. 19.  If we were not certain that this sketch was by Leonardo, we might feel tempted to take it as a study by Bramante for St. Peter’s at Rome. [Footnote 3:  See_ Les projets primitifs Pl. 43._]_

MS. P. V. 39b.  In the principal axes the chapels of MS. B. 19, and semicircular niches on the diagonals.  The exterior of the whole edifice is also an octagon, concealing the form of the interior chapels, but with its angles on their axes.

Group V.

Suggested by San Lorenzo at Milan.

In MS. C. A. 266 IIb, 8l2b there is a plan almost identical with that of San Lorenzo.  The diagonal sides of the irregular octagon are not indicated.

If it could be proved that the arches which, in the actual church, exist on these sides in the first story, were added in 1574 by Martimo Bassi, then this plan and the following section would be still nearer the original state of San Lorenzo than at present.  A reproduction of this slightly sketched plan has not been possible.  It may however be understood from Pl.  LXXXVIII No. 3, by suppressing the four pillars corresponding to the apses.

Pl.  LXXXVII No. 1 shows the section in elevation corresponding with the above-named plan.  The recessed chapels are decorated with large shells in the halfdomes like the arrangement in San Lorenzo, but with proportions like those of Bramante’s Sacristy of Santa Maria presso S. Satiro.

MS. C. A. 266; a sheet containing three views of exteriors of Domes.  On the same sheet there is a plan similar to the one above-named but with uninterrupted aisles and with the addition of round chapels in the axes (compare Pl.  XCVII No. 3 and page 44 Fig. 1), perhaps a reminiscence of the two chapels annexed to San Lorenzo.—­Leonardo has here sketched the way of transforming this plan into a Latin cross by means of a nave with side aisles.

Pl.  XCI No. 1.  Plan showing a type deprived of aisles and comprised in a square building which is surrounded by a portico.  It is accompanied by the following text:_