5 



but dark in winter, and in this respect showing a great difference. 

 Thereby even the colour of a fracture of the plant becomes rather 

 varying. On the other hand, specimens living in the litoral region, 

 on the bottom of deeper and shady rock-pools, or else in the 

 named region covered with Fucacece and other alga?, appear to 

 be less varying in colour. However, being much exposed to the 

 light, or changing strong light and shade the colour here some- 

 times seems to be even more variable than in the upper part of 

 the sublitoral region. Some specimens change their colour much 

 in drying, others less, and are, as a rule, rather fading. 



I have subsumed the genus Lithophyllum as a subgenus of 

 Litliothamnion, and the Lithothamnia proper I propose to name 

 Eidithothamnion. The former was originally established as a 

 genus bj' Philip pi 1 ), by him, however, only characterized from 

 the external shape. In the same sense Ktitzing 2 ) afterwards 

 quoted both as sections of his genus Spongites, however, species 

 of LithophyUum in some cases referred to Mastoph ova Dcsne. 3 ). 

 Areschoug 4 ) was the first, who pointed out certain peculiarities 

 in the development, and regarded Lithothamnion and LithophyUum 

 as co-ordinate genera. Rosanoff 5 ) followed him and drew more 

 thoroughly the limits between them. 



However, according to Rosanoff 1. c. and Sol ms-Lau bach 6 ) 

 there is no definite distinction in the development of the organs of 

 propagation between both the named genera. Strom felt 7 ) sup- 

 poses, that the walls of the sporangia in Lithothamnion are formed 

 all but simultaneous, but in LithophyUum successively. It is already 

 shown by Kolderup Rosenvinge 8 ) that this cannot be the 

 case. I have seen in more species of the former bearing four- 

 parted sporangia numerous not fully developed ones, and the parfi- 



r ) In Wiegm. Archiv, p. 387. 



2 ) Phyc. gener. p. 386. 



3 ) Kutz. Spec. Alg. p. 696. 



4 ) In J. Ag. Spec. Alg. II, p. 520. 



5 ) Melob. p. 97. 



6 ; Corall. Monogr. p. 62. 



7 ) Algveg. Isl. p. 22. 



%} Grenl. Havalg. p. 780. 



