358 E. R. CUMINGS POSITION OF THE MONTICI LIPOROIDS 



or Monticuliporoids. In a second j)aper (7)1 showed tliat the protoe- 

 cium, or first exotlieeal stage of the primary individual of tlie colony, is 

 very persistent in the primitive order of the Cyclostomata, and that it is 

 also very strikingly developed in the Cryptostomata {Fenestella, Polij- 

 pora, Thamniscus, etcetera). The exact form and morphological and 

 developmental significance of this feature of bryozoan development were 

 discussed at length in the latter paper. 



During the past six years I have succeeded in obtaining the desired 

 evidence in regard to the development of the Trepostomata, and have 

 worked out in detail the development of a number of genera. In the 

 case of Prasopora, Phylloporina, and CaUopora the evidence leaves noth- 

 ing to be desired. In Peronopora, Rliomhoirypa, Amplexopora, and 

 Homotrypa the protoecium has not been seen^ but the budding order is 

 definitely known. The methods of study have been described in my 1905 

 paper (7) and need not be repeated here. 



Development of Prasopora 

 the protoecium 



The proximal portion of the primary individual of colonies of Praso- 

 pora conoidea Ulr., when perfectly preserved, consists of a circular disk 

 of the type seen in the Cyclostomata and in Fenestella, etcetera (figures 

 1, 9, and 25). Its diameter is about 0.08 millimeter. As seen on the 

 under surface (figure 9), there is a slight constriction between this disk 

 and the remainder of the j^rimary individual. When the section cuts 

 through the upper portion of the protoecium and ancestrula, no sucli 

 constriction is noted. In longitudinal sections (figure 23) the protoe- 

 cium and ancestrula are seen to be continuous, although there is some 

 evidence of a diaphragm between the two (figures 23, 26). There is a 

 definite, very thin wall separating the protoecium from the substratum. 

 The lateral and superior walls of the protoecium are thickened and pre- 

 sent an appearance in the sections noticeably different from that of the 

 walls of later zooecia. This same peculiar wall structure characterizes 

 also the posterior walls of the ancestrula and primary buds. It is pos- 

 sible that the wall material of these primitive zooecia may have been 

 different from that of later zooecia, although on this point the evidence 

 is not satisfactory. In recent bryozoa, according to Barrois (1), the 

 investment of the protoecium is actually different in texture from that 

 of later zooecia. The appearance of this primitive wall substance in the 

 Trepostomata, as seen under high magnification, is precisely the same as 

 that of the proper wall of the initial portions of colonies of Fenestella, 



