III. 



ON THE STRUCTURE OF DICTYOSPHsERIA 



DECNE. 



THE genus Dictyosphceria, not to be mistaken for the widely different 

 DictyospJuzrinm Naegeli,* was founded by Decaisne,f who took Valonia 

 favulosa, Ag, for the type of it. The commonly accepted view of its 

 systematic position has remained very much the same as that indicated 

 by Decaisne, viz., near Valonia and Anadyomene, and I do not now pro- 

 pose to assign to it any other affinities, but rather to show how strongly 

 this original opinion is confirmed by an investigation of its minute 

 structure and the disclosure of an arrangement of its parts hitherto 

 undescribed. 



To the typical species of the genus, Harvey + added another, D. sericea, 

 an exceedingly well-marked species, as will presently be shown, though 

 Harvey himself subsequently seems to have doubted it, from an imperfect 

 understanding of its structure. MM. Millardet and Montagne II added 

 another species, D. Enteromorpha, I have not seen a specimen of this 

 species, and it is very difficult to say from the illustration whether it is 

 to be regarded as a true Dictyospkceria or not. Finally, Zanardini 11 

 added a fourth species, which I have no hesitation in excluding from 

 the genus on the ground that it is plainly an imperfect Valonia.** 



* Einzellige A I gen, p. 72. 



t Class, des Algues, Ann. Set. Nat., 2 sdr., vol. xvii., 1842, p. 328. 



Trans. R. Irish Acad., xxii., p. 565, and Fl. Tasin., ii., p. 339, tab. 196 A. 



Phycologia Australica, vol. v., Synopsis, p. lix. 



|| In Maillard, Notes sur File de la Reunion Algues, p. 4, plate xxv. 



H Iconogr. Phycol. Adriat., p. 73, tab. xviii. 



** Dr. Schmitz of Greifswald writes in confirmation of this view : ' D. valonioides 

 Zan. ist (wie ich durch eigene Untersuchung von Material aus Neapel feststellen 

 konnte) nichts anderes als ein unregelmassiges Regenerationsprodukt eines alten 

 halbzerstorten Exemplares von Valonia macrophysa? 



16 



