PLATE XIV. 



FA VIA FRAGUM (Esper). 



-A somewhat later larval stage than that represented on PI. XIII, fig. 104. The Edwardsian mesenteries are 



complete, but the fifth and sixth pairs have not reached the stomodseum. 

 -A young polyp, about a week after settling, with six equal entocoelic tentacular prominences; viewed fn mi 



above. 

 -Another young polyp, showing six tentacular prominences. About a week after settling. 

 -A young polyp about three weeks after fixation. Tentacles were visible under certain conditions of 

 expansion, but not in the preserved preparation from which the drawing was made, having evidently 

 become part of the polypal wall. The four irregular dark patches associated with the two lateral 

 complete mesenteries on each side represent the mesenterial filaments. The six oval lighter areas 

 within the primary entocu'les indicate tic- place of origin of the six primary septa. 



Fig. 109. — A much later larval polyp, viewed from above. The twelve prototentacles are already established, and 

 an additional tentacle has appeared within the dorsal and middle interspaces on each side. Transverse 

 sections of the same polyp (p. 509) reveal that a pair of metacnemes has arisen on the column wall, 

 within the dorsal and middle exoccele on each side, so that the additional tentacles are outgrowths of 

 the entocoeles of the new pairs of metacnemes. The entocoelic metatentacles, like the prototentacles, 

 thus arise in advance of the exoccelic members i p. 432 I. 



Fig. 110. — Vertical tangential section of the young decalcified polyp represented in fig. 108. The four complete 

 mesenteries are seen in their vertical extent, and in such a section divide the polyp cavity into five 

 chambers. The basal ectoderm (calicoblasf layer) which produces the basal plate has almost disap- 

 peared. X 70. 



Fig. 111. — The right half of the same section more highly magnified. Remnants of the calicoblast ectoderm are seen, 

 along with feeble desmoidal processes, especially at the basal extremity of the mesenteries. X 300. 



Fig. 112. — Transverse section through the stomodseal region of a larva taken from a preserved fertile polyp; the 

 dorsal surface is lower and the ventral is upper. Only three pairs of mesenteries are developed, one 

 pair of which is complete; pair II, II is better developed than pair III, III. Cell debris and free 

 zooxanthellse are seen in the larval cavity, now well established. The "Reflected ectoderm'' is well 

 shown on the endodermal side of the stornodanim. X -50. 

 626 



