EUCRATKA 13 



growth. The two arc essentially identical in struc- 

 ture. 



The creeping base exhibits some curious modifications 

 in this genus. When it is developed on the stems of the 

 more slender Algae, it consists universally, so far as I have 

 seen, of lines of decumbent cells, from which the erect 

 shoots rise, originating, like the ordinary branches, a little 

 below the aperture. But in other cases I have found it 

 assuming the form of a delicate tubular fibre, like that of 

 Aetea, which at intervals swells out into small clavate 

 enlargements, from which the cells arise. I have never 

 seen the passage of one of these conditions into the other ; 

 but it is difficult to avoid the conclusion that they are 

 morphologically equivalent, and that the clavate enlarge- 

 ments are merely aborted cells. They are frequently 

 much attenuated in Eucratea, sometimes almost oblite- 

 rated ; and in such cases we have an indication of the way 

 in which the chain of adnate cells passes into the per- 

 fectly simple tube. Under E. chelata I have described 

 a curious variety, in which the decumbent condition of 

 the zoarium appears to be permanent. 



Two species of Eucratea, as now defined, have been 

 described. One of them, E. ambigua, D'Orb., which 

 closely resembles the present form, is a native of South 

 America. E. chelata has a wide distribution in Europe, 

 while in Australia it is exceedingly abundant, attaining a 

 size and beauty which are unknown in our seas. 



Busk has described a Polyzoon from Madeira under the 

 name of Scruparia ( = Eucratea) diaphana* ; but, from 

 its mode of branching and the size of the aperture, it 

 would seem to be more properly referable to some other 

 genus. 



* Quart. Journ. Micr. So. (n.s.) Tiii.,Zoophytol.281, pi. xxxi. flg. 1, la. 



