It is thought that in the celebration of worship one of these chambers was designed for men and the other for women. Sometimes separate passages to the chapels and distinct entrances to the Catacombs seem intended to facilitate this separation of the sexes. Sometimes three, or even as many as five, _cubicula_, as in one example in the Catacomb of St. Agnes, were placed on the same axial line, and formed 27 one continuous _suite_ of chambers. The accompanying section of what is known as “The Chapel of Two Halls,” in the Catacomb of St. Prætextatus, illustrates this: A is the main gallery, D a large _cubiculum_ known as “The Women’s Hall,” to the right, and to the left B, a hexagonal vaulted room with a smaller chamber, C, opening from it. The length of the entire range from G to F, according to the accurate measurement of M. Perret, is twenty-three and a half _mètres_, or nearly seventy-seven feet. The larger engraving (Fig. 11) gives a perspective view looking toward the left of the hexagonal chamber, (D. Fig. 10,) and the smaller one, C, opening from it. By means of these connected chambers the Christians were enabled in times of persecution to assemble for worship in these “dens and caves of the earth,” surrounded by the slumbering bodies of the holy dead. [Illustration: Fig. 10.--Section of Gallery and Cubicula.] [Illustration: Fig. 11.--Perspective of Lower Chamber in Fig. 9.] 28 [Illustration: Fig. 12.--Vaulted Chamber with Columns.] The _cubicula_ had vaulted roofs, and were sometimes plastered or cased with marble and paved with tiles, or, though rarely, with mosaic. These, however, were generally additions of later date than the original construction, as were also the semi-detached columns in the angles, with stucco capitals and bases, as indicated in Fig. 9, and shown more clearly in the following engraving, which is a perspective view of the lower chamber in Fig. 9. The walls and ceiling 29 were often covered with fresco paintings, frequently of elegant design, to be hereafter described.[15] Sometimes, as in some examples in the Catacomb of St. Agnes, _tufa_ or marble seats are ranged around the chamber, and chairs are hewn out of the solid rock.[16] These chambers were used probably for the instruction of catechumens. Occasionally the _cubiculum_ terminates in a semicircular recess, as in the upper chamber in Fig. 9. These probably gave rise to the _apse_ in early Christian architecture, of which a good example is found in the Church of St. Clement, one of the most ancient Christian edifices in Rome. Niches and shelves for lamps, an absolute necessity in the perpetual darkness that there reigns, frequently occur, such as may be seen in Italian houses to-day. Without the least authority, some Roman Catholic writers have described these as closets for priestly 30 vestments and shelves for pictures. [Illustration: Fig. 13.--Cubiculum with Arcosolia.]