60 SEAWEEDS 



but of equal size and susceptibility to conjugation 

 during motility. 



This small order is of limited geographical range. 

 Zanardinia collaris, the only species of the genus, 

 occurs in the warm Atlantic (Europe and America) 

 and in the Mediterranean, while the few species of 

 Cutleria have a wider range north and south, C. 

 multifida being a native of the North Atlantic as 

 far north as Britain and Scandinavia. 



DlCTYOTACE^E. 



General Characters. The Dictyotacece resemble the 

 Cutleriaceoc in the non-conceptacular nature of the 

 reproductive organs, and in these being of three 

 sorts female, male, and non-sexual. Paraphyses 

 occur on the thallus, though not directly in asso- 

 ciation with the reproductive organs. While all the 

 reproductive bodies of the Cutleriacew are ciliated, 

 those of the Dictyafacew are all unciliated. No ob- 

 servation of fertilisation has been made in the case 

 of the bodies presumed to be male and female, and 

 this character is ascribed to them on comparative 

 grounds. The growth of the thallus, which in 

 general habit resembles that of the Cutleriacew, is not 

 trichothallic, but by an apical cell (Didyota) and by 

 groups of equivalent meristematic cells in the other 

 genera, although in their earlier stages Taonia and 

 Dictyopteris at least have, like Dictyota, an apical 

 cell. 



The Thallus of Dictyota, Zonaria, Taonia, 



