120 SYNOPTIC COLLECTION. 



account of their shape, in the erect portion of Section 3) 

 resembles Paralcyonium. The colony is supported by 

 a short stem which is often without zoons and broad- 

 ens out into several lobed masses which are thickly 

 covered with coral animals. This genus is sometimes 

 imbedded in sand while other species attach themselves 

 to the stems of plants. 



Ammothea nitida Verr. (No. 170), may have finger-like 

 projections extending from a flat base. The zoons in 

 this case are not retractile. 



Spongodes celosia Less. (No. 171), is a colonial form in 

 which the cortex of the stem and branches contains large 

 spicules. The zoons are not retractile and their tops are 

 protected by spindle-shaped spicules. 



Virgularia (No. 172) bears the zoons nearly sessile on 

 the central stem. This genus with the one that follows, is 

 among the simpler forms of the Pennatulidae and they 

 are both found in deep water. Kophobelemnon (No. 

 173,^. stelliferum O. F. Mull.) has the central stem 

 thick and bears large retractile zoons. 



The more complex Pennatulidae are represented by Pen- 

 natula aculeata Dan. & Rev. (No. 174), Pennatula phospho- 

 rea Liijn. (No. 175), and Pennatula rubra Ellis (No. 176). 

 In this genus there is a long central stem with well 

 developed zoons on more than a half of its length. The 

 stem is deeply grooved on the dorsal side and the lower 

 portion is sunk in sand and mud. These zoons are 

 dimorphic, some being sexual and others without repro- 

 ductive organs. 



In Renilla, (PI. 177 ; Nos. 178, 179), the sexes are dis- 

 tinct and the eggs and spermatozoa are discharged at the 

 same time, fertilization taking place in the water. It is 

 interesting to note that the segmentation of the egg is so 

 extremely variable "it is safe to say no two eggs ever 

 develop in precisely the same way." 



The following life history illustrates the good results 

 which may be obtained when naturalists cooperate for a 



