Anatomy of Gorgomd^. 159 



tions of Tubipora" in which many details of structure are 

 given, there is no mention nor figure of nematocysts. 



Hence it seems likely that these thread cells are by no 

 means a constant feature of Alcyonaria, being wanting in 

 certain groups, e. g., Gorgonida?, and rare in others, e. g., 

 Alcyonidee. Taking the Alcyonaria as a whole, nem- 

 atocysts seem to be more frequentl}' absent than present, 

 hence their use as a diagnostic feature is unfortunate, as is 

 also the use of a nomenclature implying their presence. 



That this use and nomenclature is largely adopted, the fol- 

 lowing will show : 



In the preface to Gegenbaur's Comparative Anatomy, E. 

 Ray Lankester divides the "Grade" Ccelentera into two 

 "Phyla," namely, Porifera and Nematophora.' The 

 former includes, of course, the Sponges and the latter Coelen- 

 terates including the Alcyonoids. 



The same writer gives the same classification with the same 

 misleading use, of the name '■'•Nematofhora''' in the article 

 "Hydrozoa" in the Encyclopaedia Britannica. 



Under the head of "Zoology" in the same encyclopaedia, is 

 given an "example of the most recent genealogical classifica- 

 tion." E. Ray Lancaster again makes the same use of the 

 name '■'■Nematofhora''' as applied to the "Phylum" of Coelen- 

 tera excepting the Sponges. 



Gegenbaur, in the body of his work on Comparative Anat- 

 omy, includes all the Coelenterates except Spongi^ under the 

 AcALEPH^,' and says, "The urticating capsules (nemocysts) 

 are special differentiations of the epithelial elements which are 

 found in all the Acaleph/E, although they are not confined to 

 them."' 



Claus and Sedgwick include the Porifera among the 

 Ccelentera and divide the latter into two sub-groups; one of 



1 "Elements of Comparative Anatomy" by Carl Gegenbaur, p. XVI 

 (preface). 



2 "Elements of Comparative Anatomy," p. 90. 



3 Idem, p. 103. 



