HYDROIDA II 



present concerning this distinguishing feature; our knowledge is, in reality, so insufficient that the 

 greatest care should be exercised in answering for species even where this character has been noted, 

 after superficial study, as the only point of difference in comparison with the nearest related species. 

 It is clear, that in certain species, the gonothecae of the one sex (the female) appear aggregated as 

 scapus or coppinia, while those of the other sex (the male) occur singly. Even though we may not 

 at present possess definite proof, it is nevertheless highly probable that also certain Lafoeida may have 

 unisexual colonies; in such case, however, the occurrence of the gonothecse singly or in aggregates 

 will even fail us as a specific character. Obviously then, in the present imperfect state of our know- 

 ledge as to the gonangia of the different species, the feature in question must be discarded altogether 

 as a generic character. Until we know more about the matter, it will certainly be most correct to 

 disregard the question of gonangia entirely when drawing the limitations of the various genera. 



Gen. Lafoea (Lamouroux). 



The colony consisting of upright rhizocaulome formations, or creeping, with tubular or narrow 

 bell-shaped hydrothecse. The hydrothecae are without diaphragma or opercular apparatus, stalked or 

 sessile, in the latter case separated from the stolon by a more or less marked constriction; where the 

 hydrotheca lies adjoining the stolons, it is possible to distinguish between the wall of the hydrotheca 

 and that of the stolon. 



A whole series of species belonging to this genus have been described from the northern seas, 

 and many of them are based on the distinction as to whether the colonies are creeping or upright, a 

 character which, as we find on closer investigation, can only be applied with the greatest caution. 

 It has long been recognised that Lafoea dumosa may either occur as a creeping form, or may form 

 upright rhizocaulome colonies; this fact in itself should be sufficient to point the necessity of careful 

 consideration, and a closer study of the northern species reveals the fact that one and the same spe- 

 cies may at times occur creeping, at others form upright colonies, when some few stolons emancipate 

 themselves from the underlayer and thus form a suitable substratum over which other stolons 

 may creep. 



Another feature in the Lafoea species which renders their limitation exceptionally difficult is 



their extrordinary power of variation. Such variation is evidently due in part to the influence of 



physical conditions in their environment, which have led to the formation of gigantic arctic forms, or 



heavily built, robust cold-water forms. Critical study of the very extensive material available has thus 



ed to considerable reduction in the number of species. 



Lafoea dumosa (Fleming) L. Agassiz. 



1828 Campanularia diimosa, Fleming, A History of British Animals, p. 548. 

 1860 Lafoea dumosa, L. Agassiz, Contributions to the Natural History of the United States, p. 351. 



Colonies creeping or upright, irregularly branched and stiffly built rhizocaulome formations. 

 Hydrotheca^ developed slightly asymmetrically, tubular, with slightly outward curving margin; they 



