ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
107 
Porphyrodiscus, a new Genus of Floridese.* * * § — Under the name 
Porphyrodiscus simidans g. et sp. n., Mr. E. A. L. Batters describes a 
seaweed from rocks near low water-mark, Berwick. The genus, which 
is intermediate between Hildenbrandtia and Hsematocelis , is thus diag- 
nosed : — Fronds crustaceous, forming smooth firm cartilaginous roundish 
expansions, closely adhering to the substratum by the entire under 
surface ; cells small, of nearly the same size in all parts of the frond, 
firmly united into a pseudo-parenchymatous layer ; tetraspores regularly 
zonate, formed in external hemispherical or flat wart-like protuberances 
(nematheces). Paraphyses wanting or not observed ; cystocarp unknown. 
Melobesiaceae.t — Herr F. Heydricli replies to the strictures of 
Foslie,J and gives further particulars respecting the structure and classi- 
fication of these Algos. The genus Sporolithon is maintained, and 
several new species are described. It differs further from Lithotliamnion 
in the tetrasporanges being divided crosswise instead of in a row. 
Another new genus, Fpilitlion, is proposed, founded on Corallina mem- 
hranacea , and distinguished from the remaining Meiobesiaceas in the 
tetrasporanges being placed in sori and not in conceptacles. The 
following is the complete diagnosis : — Thallus crustaceous, epiphytic on 
larger Algae ; at first roundish, afterwards confluent, completely coalesoent 
by its under side to the substratum, often lobed at the margin, reddish 
or whitish ; composed of either a single layer of cells radiating dichoto- 
mously, or of two layers, of which the lower one consists of large rect- 
angular cells, while the upper layer is but little developed. In the 
neighbourhood of the sorus the thallus is composed of from two to four 
rows of cells. Cystocarps and antherids in conceptacles ; tetrasporanges 
in sori, divided in a row. 
Nuclear Division and Fertilisation in Fucus.§ — The examination 
of several species of Fucus has demonstrated, according to Prof. E. 
Strasburger, that in the oogone-nucleus the reduction in the number of 
chromosomes always takes place during the first process of division, 
after the pedicel-cell has been cut off. There is always a distinct 
eentrosome. After the division of the nucleus into four, which imme- 
diately follows the reduction in the number of chromosomes in the 
rudimentary oogone, a long period of rest occurs, until the oogone has 
attained its full size, when the formation of eight nuclei immediately 
takes place. The oospheres, when they escape from the oogone, are 
without a membrane. In the process of fertilisation the antherozoid 
nucleus is not larger than the nucleole of the oosphere nucleus, but the 
latter has a much looser structure, and contains only a small quantity of 
chromatin. Shortly after the entrance of the antherozoid, its protoplasm 
appears to unite with that of the oosphere, and only the nucleus continues 
its passage, coalescing with the nucleus of the oosphere as soon as they 
come into contact. The male nucleus probably carries with it a centro- 
some, but it is too minute for this to be determined with certainty. 
Unimpregnated oospheres of Fucus did not in any case germinate, and 
* Journ. of Bot., xxxv. (1897) pp. 439-40. 
t Ber. Deutsck. Bot. Gesell., xv. (1897) pp. 403-20 (1 pi.). Cf. this Journal, 
1897, p. 225. % Cf. this Journal, 1897, p. 417. 
§ Jahrb. f. wiss. Bot. (Pfeifer u. Strasburger), xxx. (1897) pp. 351-74 (2 pis.). 
