THE ANTHOZOA 



we find dimorphism occurring in individual species of many 

 families which in other respects are widely separated from one 

 another. Only in one group, the Pennatulacea, is dimorphism of 

 constant occurrence. 



Much attention has been paid to the skeleton of the Alcyon- 



Fio. IV. 



1. — Transverse section throngh Uie stomoclaeiim of Funiculxna q^iadrangvlarif. sc, sulcus. 



•-'.—Transverse section of the same species below the level of the stoniodaeuni. scvx, sulcar 

 mesenteries; asrnx, asulcar nie.senteries. 



3. — Longitudinal section of a tentacle of AXcyoninw, digitatum. ec, ectodenn with ectodemiic 

 ner\'e plexus; mg, niesa};lo«*a ; eii, endodenn. 



4. — Transverse section through a portion of a mesentery of i^/ri/on in m diijitatitm, showing 

 the large retractor muscle fibres borne on branched processes of the nie.sogloea, and the delicate 

 protractor muscles on the opi>osite face of the mesentery. 



.5. — Transverse section through one of the sulcar mesenterial filaments of w4/i-i/oniMm rfiyi- 

 tatum, showing the glan<l cells, ijr, and the Hagellat<> cells, /o. 



6.— Transverse section through an asulcar filament of the same species, showing the ojien 

 groove lineil by elongate ciliattHl ectaienn cells. 



7, 7a, ~l>, 7r, "(/. — Myoepithelial cells from the endoderm o( Alcyonium diffitatum. 



8. — Two nematocysts of AU-nonium digitatum. (1 and 2 original ; the rest after Hickson.) 



aria, but for taxonomic purposes it is of subordinate value. A 

 calcareous skeleton is present in all, with the exception of Proto- 

 caulon, Cornularia, some species of Clavularia, and Monoxenia, 

 and it is possil)le that spicules so minute as to have been over- 

 looked are present in these forms. The calcareous skeleton 



