of the Anthozoa Tabalata. 7 



project into the interior as longitudinal ribs Laving the appear- 

 ance of septa. It is possible that these longitudinal ribs are 

 connected with the cleavage of the cells into two or more — a 

 mode of increase which is shown by sections to have often 

 occurred, though it is difficult to see why some cells should 

 have grown to such a length without fission taking place. Good 

 information on these points can be gathered from an elaborate 

 paper by Rominger*, who, as early as 1866, stated his opinion 

 that ChceteteSy Montlculi'pora^ and other related forms were 

 referable to the Bryozoa, though he had had no opportunity 

 of observing how they had grown out of Discoporella and 

 Ceramopora. Each cell is now surrounded by a mass of small, 

 vertical, circular or polygonal tubes, having the appearance 

 of a ooenenchyma. Consequently the surface of the poly- 

 zoarium quite resembles that of Heliolites^ next to which genus 

 Fistidipora has also been ranged. At regularly distant points 

 there are smooth patches without any cells. Such jjatches 

 are in vain looked for in the true Heliolitida ; and in these 

 there are moreover generally twelve septa, with which the 

 longitudinal ribs of the Fistulipora, variable as they are in 

 place and number and often wanting, can in no way be con- 

 sidered homologous. All the cells, as well as the interstitial 

 tubes, are traversed by tabulae of the same incomplete type as 

 those which characterize Monticidl])ora. Finally, there is a 

 third stage in the growth of this Bryozoon. The interstitial 

 cells now become covered by a thin, smooth, calcareous mem- 

 brane, resembling that which forms the macule, leaving the 

 larger cells (or zooecia proper) open, and giving their orifices 

 a new shape. They become circular or oval, with a nmch 

 thicker wall than before, and they project high above the sur- 

 rounding smooth surface. There is now such a dissimilarity 

 to Fistulipora^ that only the circumstance that both the Fisfu- 

 lipora stage and the one just mentioned are seen in the same 

 polyzoarium could convince one that they are really only dif- 

 ferent stages of growth of the same species. This third stage 

 I have called the Tliecostegites stage, in consequence of a 

 certain likeness to the genus Tliecostegites^ which caused 

 Ferd. Roraer to include this Bryozoon in that genus. This 

 phase of growth more often changes into a Monticulipora than 

 does the preceding or Fistulipora stage. The Monticulipora 

 thus produced is remarkable for its regular "monticules," 

 arranged in quincunx, and formed at the points where seven 

 or eight large cells are clustered, just as in M. petropolitana^ 



* " Observations on Cluetetes and some related Genera, in regard to 

 their Systematic Position, with an appended Description of some new 

 Species," Proc. Acad. Nat. Sci. Philad. 18G6, p. 11.3. 



