28 Coelenterata. 



polyps (nematozooids). Being absent in some species they have undergone 

 retrogression as in some other species many of them are very small being 

 formed only of a mere group of nematocysts. From a study of the mode of 

 origin of the polyps and lateral branches the author concludes that the an- 

 cestral form possessed a stem on which the polyps and lateral branches 

 were formed only along a narrow longitudinal strip. This laterality is possibly 

 due to the fact that the ancestor formed a creeping stolon which after acquiring 

 an axis became erect. In the former condition the stolon would bear polyps 

 only on the upper side and this possibly accounts for the laterality above 

 named. The softness of the ccenenchyme and the small number of spicules 

 are probably secondary characters of Lepidogorgia and Chrysogorgia acquired 

 in the deep sea in the waters of which only a small amount of calcium carbo- 

 nate is dissolved. The numerous nematozooids in many species will afford 

 a better protection against enemies than would spicules. Some species which 

 have lost their nematozooids still persist as, in the deep sea, their enemies are 

 few. From a comparison of the length of the internodes in young and old 

 stems the author concludes that apparently only the last interne de grows in 

 length and therefore only in this part can the coenenchyme elongate in Chrys. 

 Descriptions are given of Lep. 5, Chrys. 36 (14 n.), Metallogorgia n. 1, Irido~ 

 gorgia 1, Pleurogorgia n. 1, Eiisea 1. See also Versluys( 1 ). 



(C. Hydrocorallia.) 



