362 E. R. CUMINGS POSITION OF THE MONTICULIPOROIDS 



that this lamina does not consist of a basal membrane or epitheca that 

 has risen up into the colony. 



Development of Callopora 

 the protoecium 



The protoecium of Callopora has the same form and appearance as 

 that of Prasopora, described above. It has been seen in several speci- 

 mens, two of which are figured (figures 7 and % = Callopora dalei). 

 Both of these zoaria were growing on the shells of brachiopods, attached 

 to the plicated outer surface of the shell, as shown in figure 39, where 

 one of the shell plications is seen at the bottom of the figure. This 

 accounts for the somewhat irregular arrangement of the primary buds, 

 since they were not all developed on the same plane, but on an uneven 

 surface. The protoecium in figure 7 was attached to a plication, most 

 of which was, of course, ground away in sectioning down to the protoe- 

 cium itself. The striated appearance of the section to the left of the 

 protoecium is due to the presence of an excessively thin remnant of the 

 brachiopod plication. This serves to call attention to the fact that the 

 section reveals the absolute point of attachment of the primary individual 

 of the colony. A similar feature is shown in figure 8 of another speci- 

 men. Tlie relations of the protoecium and ancestrula are exactly the 

 same as already described in Prasopora. The Avail structure is also of 

 the same type as in the latter genus. 



THE ANCE8TRULA 



The ancestrula is well shown in figure 7. It is long, tubular, and very 

 prone on the substratum. There is a very slight constriction between the 

 ancestrula and the protoecium. As seen on the upper surface of the 

 section, the walls of the two are perfectly continuous. The section 

 shown in figure 8 was purposely left thick in order to show this feature. 

 The surface shown in the figure is the lower surface, which was attached 

 to the substratum. An exceedingly thin remnant of the brachiopod 

 shell to which the protoecium and ancestrula were attached is present. 

 By focusing up and down on this section the relations of the two can be 

 very satisfactorily made out. The ancestrula is seen to be an obliquely 

 placed, simple tube, with a disk-shaped proximal portion — the protoe- 

 cium. The two have the same diameter, which is about 0.08 millimeter. 

 As seen in figures 7, 8, 16, and 38, the initial zooecia in Callopora are 

 all at first very nearly parallel with the substratum — that is, they lie, as 

 in Prasopora, prone. For this reason the ancestrula is cut obliquely in 



