MorpTiologi/ of the Madreporaria. 



U7 



Cladocorn arhuscula, already described, that undoubtedly t'ley 

 possess the same si^^nificaiice — that is, they are poly|)s whose 

 exceptional ellla^^•ellH■llt will ultimately result in tissiou. 

 When this is reached, the two daughter polyps will be each 

 provided with two pairs of directives, and exactly resemble 

 bud-polyps in their cyclical and liexameral regularity. 



Fi?. 4. 



Diagrammatic representation of the mesenterial arrangement in four 

 different polyps of Slephannccenia inf.ersepta (Esper). a, as found in 

 most mature polyps of a colony ; b-d, as met with in three enlarged 

 polyps. 



A transverse section through the lower stomoda^al region 

 of a retracted polyp of Solenastrrea hyades (Dana) is repre- 

 sented somewhat diagrammatically in tig. 5 a. Six pairs of 

 mesenteries, including a pair of directives at opposite extre- 

 mities, extend as far as the stomodajum, and six alternating 

 pairs are incomplete, and constitute a second cycle. The 

 septal invaginations — entocoelic ani exocoelic — are also 

 displayed, and at this level they are grou[)ed in threes, by 

 the union of the entoseptum within each pair of the second 

 cycle mesenteries with the adjoining exosepta — one on each 



