212 C. E. Beecher — Development of a Paleozoic Poriferous Coral. 



If the preceding interpretations of structure and affinites are cor- 

 rect, a simple, conical imperforate, non-tabulate prototype, or proto- 

 corallum, may be assumed for the Madreporaria Perforata. The 

 next derived form, represented by the early nealogic stages of P. 

 lenticxdare^ has the structure and growth of Aulopora, and consists 

 of the parent cell with one or more buds. At this stage, which may 

 be called the Atilopora-stage, the initial eorallite has the same num- 

 ber of mural pores as developed buds, for each bud leads into the 

 parent cell by a basal opening or pore. Aulo^yora may thus be con- 

 sidered as representing a primitive type of a poriferous coral, in 

 which the number of pores in each eorallite corresponds to the num- 

 ber of buds given off plus one connecting it with the pai*ent cell. 

 Some species of this genus are free throughout most of their growth 

 [A. subtennis, Hall), agreeing closely with the erect growth of 

 Pomingeria and Syringopora. This fact removes one of the im- 

 portant arguments against the relations of Aulopora with these 

 genera. The corallites of Aulopora usually send off buds before 

 turning out of the common axis of the branch or colony, after which 

 no gemmation commonly takes places. By the explanation here 

 advanced, this lack of a tendency to gemmation in the distal por- 

 tions of the corallites in this genus accounts for the absence of 

 mural pores when such portions are in contiguity. The periods of 

 gemmation in Pomingeria are periodic. Several buds, often tonn- 

 ing a verticil are given off from the parent eorallite. Considerable 

 elongation of the tubes takes place before other series of buds are 

 produced. The budding is prolitic at these points, and here also 

 occur the mural pores. The latter are therefore developed when 

 the period of gemmation is in force. If pores are formed elsewhere 

 when the corallites happen to come into juxtaposition, it may pos- 

 sibly be explained as the result of a stimulus produced by the con- 

 tiguit}' of the animals. Further observations are necessary to show 

 that pores exist at other places than the bases of the verticils or 

 points where numerous buds are given oft' and where from crowding 

 the corallites are in juxtaposition. 



It therefore seems, that, primarily, the development of nuiral 

 pores is identical or homologous with the process of gemmation. 

 Whether this cause is operative in such forms as Golumnopora or 

 Alevopora yet remains for investigation. The porous condition of 

 the walls in these genera may be an inherited character Avithout an 

 active exciting cause, or it may be teleologically different. 



Tale Museum, New Haven, Conn., May 20th, 1891. 



