PROBLEM OF THE MONTICULIPOROIDEA 1 9 



rarely in a growth retardation stage. A few young cells or 

 mesopores are present, or many mesopores, or again ■ aggre- 

 gated mesopores between the cells are found in some species, 

 or exclusively mesopores form maculae or large aggregates in 

 other species, with or without surrounding major-sized autocells. 

 The elevated clusters are the typical monticules. The extreme 

 degree of elevation is expressed by the name monticule. Mac- 

 ulose ones or "maculae" are nearer plane or slightly depressed. 

 Exceptionally a typical monticule may extend like a ramulet, in 

 which case it is probably to be considered as such, — a fortui- 

 tous acrogene growth having sprung from the area of one monti- 

 cule as it might also have from that of several. 



The monticules are distributed on the zoarial surface more or 

 less regularly, new monticules arising from the widening inter- 

 vals, and never, apparently, one monticule from another. The 

 function of the zooids that built the major autocells is unknown 

 if it was different from that of others. The only discernible 

 peculiarity of the monticules to which a special function could 

 be assigned is their more rapid reproduction or cell increase 

 than the interspaces. In this respect they resemble the acro- 

 gene growths or the axial region, and when very prominent they 

 might suggest an origin as retarded branches, but no unques- 

 tionable transitional forms to these are known to me. They 

 differ from branches in their size and in relation to the zoarium 

 as a whole ; for, if monticules produce the more new cells, 

 their interspaces produce the less, the zoarium being unchanged ; 

 while, on the contrary, growth of branches comprises essen- 

 tially the zoarial growth as well as the maximum increase of 

 cells. 



The surface pattern, as shown, is very diverse. The average 

 size of cells in a species is quite constant, but in different spe- 

 cies differs several diameters. The form of aperture, quad- 

 rangular, polygonal, to rounded ; the relative size and numbers 

 of young cells and mesopores ; the monticules and maculae of 

 varied style ; all these form conspicuous essential characters by 

 which species can be recognized. The calycals, too, are deep 



