Madreporarian Subfamily Montiporine. 125 
are confined to the upper surface. In the case of the branched 
specimens the tips of the branches which correspond with 
the growing edge of the explanate forms consist entirely of 
the streaming layer, and this may be seen forming the axis 
of allthestems. The cortical layer, which gradually thickens 
the branches, can in most cases be seen to be formed of 
threads bending outwards at right angles to the direction of 
the axial streaming layer. 
Leaving, then, the primitive basal streaming layer, we 
have to consider the variations presented by the upper thick- 
ening layer just described :— 
(1) It may merely thicken the streaming layer gradually 
as a filamentous reticulum, the surface in which the calicles 
open remaining all the time smooth. In reference to the 
level surface, I have called this group “ glabrous,” and under 
it I have arranged some thirty different types (fig. 3a). 
(2) The thickening reticulum may grow faster than the 
calicles, causing the interstices to swell up into ramparts 
surrounding pits, in the bases of which the calicles open. I 
have called this the ‘“ foveolate” group, after the most 
extreme type, MW. foveolata of Dana. 
Between these two come specimens which are foveolate 
while in rapid growth, but eventually become smooth ; these 
I have called “ glabro-foveolate.”’ I have found some twelve 
foveolate types and five glabro-foveolate. 
One specialization of these ramparts has a curious resem- 
blance to true protuberant calicles. This appears to have 
misled Dana in his ascription of true calicles to MW. caliculata. 
(3) The thickening reticulum shoots up into papillae which 
rise up above the general surface. ‘There are several more or 
less distinct variations of the “ papillate” specialization, 
which at the moment of writing is shown by at least thirty- 
three types (fig. 3D). 
The leading differences are as follows:—(qa) reticular 
uprisings froth up the interstices over irregular patches of 
different sizes ; (4) the papille are always in some relation to 
calicles, forming hoods or mounds, on the outer faces of 
which calicles open; (c) the papille run together to form 
either nearly parallel series in the direction of growth, or 
else more or less gyrating ridges; (d) lastly, as the extreme 
type, the papilla rise as mipple- or nearly symmetrically 
dome-shaped processes scattered more or less thickly over 
the surface, but not arranged in radial series (fig. 3 6). 
(4) ‘The thickening reticulum undergoes a change in its 
texture ; the threads which bend up vertically become differen- 
tiated from the rest of the elements of the reticulum and 
