PLATE XX. 



M.'EANDRINA LAP.YRINTIIICA ( Kllis & Solandor). 



Fig. l;i.S. — Transverse section thrcmt;li the ui>per part of the polypal tis.sues covering a collinal riilge; the column 

 wall anil mesenteries on one side belcjiig to a different series of ])olyps from those on the other 

 side. The irregular parts of the corallnm incln<led are the first traces of the exsert sejita and thecal wall. 

 The septa at this level are both entoccelic and exocadie^ the former being much better developed. 

 Certain of the mesenteries are free for some distance at their inner extremity, and others are already 

 attached to the skeletotrophic tissues. The mesenteries are arranged at practically equal distances 

 apart, and no directive pairs occur. The pairs of the two adjacent .systems do not correspond. X "5. 



Fiii. TlXi. — Transverse section through the tentacular region of the same retracted colony. The middle skeletal area 

 represents the thecal wall common to two polypal systems; small exoseptal invaginations occur in 

 addition to the entoseptal. The rounded evaginations of the mesenterial siiaces represent the tentacles; 

 the entotenta<'les (en. /.) are larger than the exotentacles (cc. t.). X 75. 



Fk;. 14(1. — Section through an incomplete mesentery, and ]iart of the wall of the septal loculus in which it is inclosed. 

 Three ova and two s])ermaria occur within the mesentery. The skeletotrophic endoderm is highly 

 vacuolated, the nuclei and protoplasmic contents aggregated mainly toward the margin. X 110. 

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