74 Cumings — Development of some Paleozoic Bryozoa. 



studied. Certain persistently flabellate forms should, however, 

 be placed in appropriate genera, as suggested by Simpson." 



The number of rows of zooecia, which has been considered 

 the chief differential character between Polyjpora and Fen- 

 estella, is of altogether subordinate value. Carinse do not 

 occur in Polyjpora. It is believed that there are physiological 

 as well as developmental reasons for this. 



V. Development of Paleschara. 



Two specimens of Paleschara from the silicified Lower 

 Helderberg material show the initial region of the zoarium 

 (figs. 78-80). The protoecium is slightly larger than the other 

 zooecia and is closely surrounded by eight buds. Whether 

 these all originated from the protoecium cannot be determined ; 

 from the analogy of other Bryozoa the belief would" be justi- 

 fied that they did not. It is significant that their number and 

 arrangement are the same as in the recent genus Microjporella. 

 The zooecia numbered 1, 2, and 3 in the figures are in more 

 intimate contact with the protoecium than the others (4-8) 

 and may represent the median and lateral buds. From the 

 analogy of Microjporella, however, the median bud should be 

 lacking ; and 3 and 8 should represent the lateral buds from 

 which 1 and 2 were produced. 



VI. Conclusions. 



In general all Bryozoa, both recent and fossil, thus far 

 studied, conform to a fundamental plan of primary budding. 

 This consists in the development from the protoecium of one or 

 two lateral buds and frequently of a median bud which arises 

 somewhat later.* Any apparent departure from this plan is 

 found on closer inspection to conform to it. Fenestella, Uni- 

 trypa, Polyjpora, and probably Paleschara conform strictly to 

 this plan of budding. 



In Fenestella the primary buds arise in such a position and 

 are so orientated as to cause the apertures of all subsequent 

 zooecia to face atvay from, the axis of the zoarium. In Poly- 

 jpora the primary buds arise in such a position, and are so 

 orientated as to cause the apertures of all subsequent zooecia to 

 face toward the axis of the zoarium . This difference is taxonomi- 

 cally of family value. In certain cases the full number of buds 

 may be lacking in the metanepiastic stage, or, when present, 

 they may have an unusual arrangement, and give rise, for either 

 reason, to asymmetrically developed or flabellate colonies. Such 



* This fact will afford a solution to the systematic position of the Treposto- 

 mata, since the budding from the prototheka (irpurog + drjurj) of corals follows 

 an entirely different law. 



