THE ANTHOZOA 



parts of the ectoderm, but in most Alcyonaria subsequently become 

 situated in the mesogloea. Fig. V. represents the principal de- 

 velopmental phases of Gorgonia Cavolinii, as figured by von Koch. 



The sub-class Alcyonaria comprises many and highly diversified 

 forms, yet, as has been seen, the anatomy of the zooids is re- 

 markably constant throughout the group. The diversity of form 

 is chiefly due to the manner in which the zooids are aggre- 

 gated together to form colonies, and the mode of aggregation is 

 due, in the first place, to the mode of asexual reproduction by 

 budding. The form and nature of the skeleton and the mode of 

 aggregation of the zooids are largely interdependent, and must be 

 taken together as a basis of classification, the larger groups being 

 defined chiefly by the mode of aggregation, and their subdivisions 

 by the character of the skeleton. The difficulties of classification 

 are, however, considerable. The characters on which reliance is 

 placed are so inconstant, and shade so imperceptibly into one 

 another, that it is in many cases impossible to say where one group 

 ends and another begins. 



Nearly all the Alcyonaria are colonial, but a few solitary forms 

 have been described, and these may conveniently be placed in a 

 separate grade under the name of 

 Protalcyonacea (Protalcyonaria, Hick- 

 son), the colonial forms forming a 

 second grade, Synalcyonacea. 



GRADE A. PROTALCYONACEA. 



The Protalcyonacea are solitary 

 Alcyonarian zooids, having the struc- 

 tural features common to the in- 

 dividual zooids of the sub-class. They 

 do not form colonies by gemmation. 

 The grade contains a single family, 

 the Haimeidae, which contains three 

 genera. 



Family Haimeidae, M. Edw. Hai- 

 mea funebris, M. Edw. from the coast 

 of Algeria. H. hyalina, Kor. and 

 Daniellsen, from Norway. Hartea 

 elegans, P. Wright (Fig. VI.), from the 

 Irish coast. Monoxenia Dartvinii, 

 Haeckel, from the Red Sea. 



It may be doubted whether all 

 or any of the Protalcyonacea cited 



above are adult forms ; possibly they are the young forms of 

 colonies. The reproductive cells are neither figured nor described 



Fio. VI. 



Hartea elegans, an example of the Protal- 

 cyonacea. (After P. Wright.) 



