33 



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 vvith Fucaceæ and other algæ, 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 IAthophyllurn as a subgenus of 

 IAthothamnion, and the Lithothamnia proper I propose to name 

 Eulithothamnion. The former was originally established as a 

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

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

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

 of IAthophyllurn in some cases referred to Mastophora Des ne. 3 ). 

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

 in the development, and regarded Lithothamnion and IAthophyllurn 

 as co-ordinate genera. R osa no ff 5 ) followed him and drew more 

 thoroughly the limits between them. 



However, according to Rosanoff 1. c. and Solms-Laubach 6 ) 

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

 propagation between both the named genera. Stromfelt 7 ) sup- 

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

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

 shown by Kolderup Ros en vinge 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 parti- 



*) In Wiegm. Archiv, p. 387. 



2 ) Phyc. gener. p. 386. 



3 ) Ktitz. Spee. Alg. p. 696. 



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



5 ) Mélob. p. 97. 



6 ) Corall. Monogr. p. 62. 



7 ) Algveg. Isl. p. 22. 



8 ) Grønl. Havalg. p. 780. 



