EEPORT ON THE PENNATULIDA. 



Frotocaulon molle, Koll., 

 Cladiscas gracilis, Kor. and Dan., 



700 

 40 



39 



It follows from all these facts, as I have already pointed out in my monogra^sh 

 (])age 449), that the simpler forms of the Pennatulida, especially those with sessile 

 polyps, i]ihabit great depths. The presence of their less complex representatives in 

 deep water has also been shown in other invertebrate groups. These simpler forms are 

 probably also the oldest, and may be regarded as the last remnants of an extinct primary 

 creation. The Protoptilidee and the Umbellulidse are the principal representatives of these 

 old forms, and of these two families especially the Challenger Expedition has discovered a 

 large number of species with a wide distribution. This addition to our knowledge 

 makes it possible to gain a better insight than formerly into the development of the 

 whole group. On this point I may refer the reader to my often-quoted monograph, in 

 which the phylogenetic development of the Pennatulida is treated on the 449th and 

 following pages. 



