CYSTS AND CYSTIPHRAGMS 351 



appearance, when seen in the genera last named, have been denied the 

 name of cystiphragms and liave been spoken of as curved diaphragms. 

 We hope that we shall be able to show that in l)()th cases these structures 

 are tlio same in origin and function, and that the difference is only a 

 matter of the regularity of their occurrence. AW' sliall suggest an inter- 

 pretation of cystiphragms in the light of certain associated structures, 

 here described for the first time. 



INFUNDIBULAR DIAPHRAGMS 



The sti-iictures referred to are illustrated in liguies 1 to 22, inehisive. 

 Many years ago Ulrich (30) figured and described "infundibular dia- 

 phragms" in Amplexopora rolnista and .1. cingulata. We have not ex- 

 amined the sections on which his descriptions were based, but there can 

 be no doubt, after an examination of his figures and the figures presented 

 herewith, that he was dealing with the same structures, but failed to see 

 that the infundibular diaphragms are in reality the upper portions of 

 complete, bottle-shaped or vase-shaped cysts, and that in every case these 

 cysts inclose a mass of bro^vn granular material unlike anything ever 

 seen in any other portion of the zoarium. The brown material and the 

 cysts are never present in the mesopores of species in which mesopores 

 occur. 



CYSTS AND BROWN BODIES 



Tlie portion of the cyst that envelops these brown masses is usually 

 excessively thin-wailed and may easily be overlooked. Tt may be best 

 studied with a 4 nnn. objective in sections cut very thin (about 25 mi- 

 crons). The cyst and its narrow neck (nl- in the figures) is usually 

 I'onnd in cross-section, as shown in numerous tangential sections. Tn 

 lleterotrypa singularis and !T. suhramosa there are thousands of these 

 cysts. They are found in greater or less perfection in many other genera, 

 and especially in Amplexopora, Batostoma, Peronopora, Homotri/pella, 

 Monticulipora, Prasopora, Homotrypa, AiactoporeUa, Aiactopova, etcet- 

 era. In Homotrypa they are very rare, but in the other genera of tlie 

 family Monticuliporida' {seiisu slrichi) they are common, in many 

 cases the cyst is imperfectly developed, and tlie brown mass is then asso- 

 cialcd with I he cN si i|»hi'aL;nis and diaphiagiiis. hul alw a\ > in a \crv special 

 way. This latter ai'raiigeinrnt is best show ii in Pcrdiiiiimni (ligures IS. 

 20, 22). In forms that iioi'mally have a lai'g(> numhcr n\' cvstiiihragins 

 a |n'rfc((ly foinie(| cyst, such as is so coninnin in II I'lcrnl nj pit . is seldom 

 seiMi. 



Tiu' special rclationsliips of the brown material and the cystiphragms 

 and diaphrjignis ai'e as f(dlnw> in rcnnidjuini ((ignres IS, •jO, 22): 



