HIPPOTHOA. 287 



orbicular, with the lower margin sinuated or produced. 

 ZOARIUM adherent. 



SMITT disallows the genus Hippothoa, and ranks its 

 members with species which are supposed to possess similar 

 zooecia, irrespective of the habit of growth. Thus H. 

 divaricata is regarded as a hippothoiform variation upon 

 Schizoporella hyalina. In certain varieties of the latter 

 species the cell is attenuated and produced below, and no 

 doubt in this condition bears a considerable resemblance 

 to a somewhat gigantic Hippothoa. On the other hand, 

 the connecting fibre is sometimes much abbreviated in the 

 latter genus, and occasionally is quite rudimentary. In 

 such cases we may find indications of the way in which 

 one type has passed into the other. But as I should not 

 place S. hyalina on the strength of this occasional variation 

 amongst the Hippothoa, so I should not merge the latter 

 in Schizoporella because at times the caudate prolongation 

 of the cell is almost wanting. 



In several of the massive species we meet with varieties 

 or states in which the cells run out into single linear 

 series ; but this deviation from the normal condition does 

 not convert them into Hippothoa. In such cases the cells 

 do not usually become caudate, much less are they fur- 

 nished with the thread-like appendage which is the common 

 and typical characteristic of the latter group. These linear 

 varieties cannot be correctly designated Mppothooid. 



Universally, I believe, amongst the Hippothoa the cell 

 is narrowed below into a kind of tubular peduncle, more 

 or less extended ; prevailingly it is distinctly caudate, and 

 produced into a filiform appendage, while the remarkable 

 plan of the gemmation is constant. I think we have here 

 the characters of a natural group, sufficiently (though of 

 course not absolutely) isolated, and worthy of a separate 



