202 ROSACEA PLICATA. 



tinguishcd from R. medusa (p. 203) by the depth of the hydroecium and the 

 small nectosac. The provisional identification as plicata rests on their general 

 resemblance to the Biscayan specimens of that species (Bigelow, : lib), especially 

 in the shortness of the hydroecium of the younger nectophores. There is, 

 however, a difference in the somatocyst. 



In all the Biscayan examples of plicata the upper end of the somatocyst 

 turns dorsally, away from the dorsal face of the hydroecium which it follows 

 for the rest of its length, and its terminal region is slightly thickened ; in some 

 specimens it forms a definite egg-shaped dilation, and a more or less pronounced 

 terminal swelling has usually been described. But in the Eastern Pacific speci- 

 mens, the ascending branch of the somatocyst lies in the hydroecial wall to its 

 very tip, and there is no terminal dilation. At first sight this difference sug- 

 gested that the Pacific specimens might be specifically separate from the Atlan- 

 tic ones. But the conditions in the latter are so variable that I doubt whether 

 there is any actual discontinuity between the two; if not, the extremes would 

 at the most represent varieties of the one species. To settle the question will 

 require better preserved, and more extensive material from the Pacific. And 

 until such is forthcoming the question may be left open. 



The hydroecium in the younger nectophores (Plate 2, fig. 7) is much shorter 

 and deeper than it is in Praya cijmbiformis; as I have already noted (:11b), 

 the difference affords a good field mark, even in the case of battered specimens, 

 for the separation of the two. None of the older figures show the extent of the 

 hydroecium in the younger nectophore, or even whether there is one, though 

 Vogt ('54, pi. 17, fig. 3), has given a good representation of it in the older of 

 the two chief nectophores. But neither Kolliker nor Vogt gave detailed figures 

 of this portion of the colony, though they described the appendages fully. 



The older nectophores (Plate 2, fig. 9) are proportionately shorter and 

 broader than those of P. cijinbiformis (Plate 2, fig. 2), and their hydroecial 

 furrows much shallower, a feature probably connected with the loose associa- 

 tion of the two nectophores, shown by Kolliker and by Vogt. But this feature 

 is so often masked by distortion in preserved material that identification of the 

 separate nectophores would be difficult or even impossible unless they were 

 captured side by side with the better characterized younger nectophores to which 

 they are normally attached. In none of the specimens was there a reserve 

 nectophore, nor could I certainly identify the bud for such a structure. On 

 account of the condition of the material, no description of the appendages is 

 possible. 



