of the Anthozoa Tahulata. 7 



project into the interior as longitudinal ribs having the appear- 

 ance of septa. It is po.s.sible tiuit these longitudinal ril»s are 

 conneeted witii the eleavage of the eells into two or more — a 

 mode of increase which is shown by sections to have often 

 occurred, thougii it is ditticult to see why some cells should 

 have grown to such a K-ngth without fission taking place. Good 

 information on these points ean be gathered from an elaborate 

 pa])er 1)V liominger*, who, as early as 186(1, stated his opinion 

 that i'/ia-tetrs, Slonficnliponi^ ami other related forms were 

 referable to the IJryozoa, tiiough he had had no opj)ortunity 

 of observing how they had grown out of Discopurella and 

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

 vertical, circular or ]»olygonal tubes, having the appearance 

 of a caMienehyma. Consequently the surface of the poly- 

 zoarium quite resembles that oi llelioUtes^ next to which genus 

 FistuUpora has also been ranged. At regularly distant points 

 there are smooth patches without any eells. 8uch jjatches 

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

 there are moreover generally twelve septa, w^ith which the 

 longitudinal ribs of the Fiatulipora, 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 tabulai of the same incomplete type as 

 those which characterize MonticuUpora. 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, resemblins: that which forms the macuhe, leaving tiie 

 larger cells (or zocecia proper) 0])en, and givmg then" orihces 

 a new shape. 'I'hey become circular or oval, with a nmch 

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

 rounding smooth surface. There is now such a dissimilarity 

 to Fistuli'pora, that only the circumstance that both the Fistu- 

 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 tliird stage 

 I have called the Thecostegites stage, in consequence of a 

 certain likeness to the genus Thecost€(jiies, which caused 

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

 phase of growth more often changes into a Montirulipora than 

 does the preceding or FistuUpora stage. The MonticuUpora 

 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 Cha-Utet and wnie related (Senera, in rejrard to 

 their Systematic Position, with an appended Description of some new 

 Species','' Proc. Acad. Nat. Sci. PhiLid. !>>(>(>, p. 113. 



