F. R. Cumings — Development of Fenestella. 173 



of a secondary bud, and may be compared with figure 53, which 

 is a drawing of two zooecia of Protocrisina (after Ulrich), a 

 cyclostomatous bryozoan from the Trenton. The resemblance 

 is too striking to need further emphasis. No internal zooecial 

 structures have been observed in the secondary buds. 



Tertiary and Later JBacls. 



One bud of the third generation from the ancestrula occu- 

 pies a position in the first tier of zooecia, diametrically opposite 

 the ancestrula (777, figs. 6-13, 24, 26, 43, 54-58). the shape 

 of this bud is well shown in figures 37, 45, 59, and 60. There 

 is no means of telling from which of the two secondary buds 

 this tertiary one is derived. It may have originated now from 

 one, now from the other. In figure 43, it is rather more inti- 

 mately associated with 32, which was in turn derived from the 

 right lateral primary bud. Figure 13 indicates that each of 

 the secondary buds gives rise to a median bud lying in the 

 second tier of zooecia. 



Ascending the axis of the zoarium (figs. 17-20, 36-39), there 

 is exhibited a series of zooecia very symmetrically arranged 

 about the axis. In transverse sections, above the level of y, 

 figure 17, these present a peculiar star-shaped appearance seen 

 in figures 15, 16, and 58, as well as in figure 61 of the writer's 

 former paper. The order of budding of these later zooecia 

 cannot be determined, although the writer has devoted a large 

 amount of time and study to this point. It is probable that 

 the order of budding in these later generations is without sig- 

 nificance. An important point shown by the sections, how- 

 ever, is the shape and size of these zooecia. This is best seen 

 in figures 17 and 38. The zooecia are tubular, but somewhat less 

 elongate than the earlier ones. It is not until the zoarium 

 begins to expand into its characteristic infundibular form that 

 the zooecia assume the shape normal to Fenestella. Figure 51 

 shows a row of zooecia from the neanastic region (base of the 

 cone) of the specimen represented in figure 38. For compari- 

 son with this is inserted figure 52, showing a. specimen of 

 Fenestella acmea from the Waldron shale of Tarr Hole, Indiana. 

 The resemblance is striking. The adult zooecia of the Thed- 

 ford Fenestella are shown in figure 49. 



Discussion and Conclusions. 



The morphological element of the bryozoan colony which 

 corresponds to the primitive integument of Mollusca, Brachio- 

 poda, etc. (that is, to the protoconch, protegulum, etc.), is the 

 protascium, or basal disc, of the primary individual of the 

 colony. The protoecium is the calcareous or chitinous wall of 



