ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1023 



Algae. 



Fertilization of Fucus.* — Herr J. Behrens has closely followed 

 out the structure and development of the sexual organs, and the mode 

 of fertilization, in Fucus vesiculosus. 



In the male conceptacles the mother -cell of the antheridium is 

 distinguished from the vegetative cells of the paraphyses by its more 

 abundant protoplasm, almost entirely destitute of vacuoles. It con- 

 tains small disc-shaped chromatophores which continue to divide 

 until the antheridium is ripe. The nucleus divides continually with 

 the ordinary karyokinetic figure, until sixty-four nuclei, the future 

 antherozoids, are formed. Each mature spermatozoid contains a 

 nucleus composed chiefly of chromatin ; the yellow spot is a chroma- 

 tophore which has lost its colour. The cilia are derived from the 

 envelope of protoplasm which incloses the nucleus. The antherozoid 

 is therefore a perfect naked cell. The wall of the antheridium is ulti- 

 mately composed of two layers, the outer of which becomes resolved 

 into mucilage at its apex, through which the inner layer bursts and 

 is driven out of the conceptacle, ultimately becoming itsejf converted 

 into mucilage to allow the escape of the antherozoids. 



The mother-cell of the oogonium contains a nucleus with a single 

 remarkably large nucleolus and a comparatively small quantity of 

 chromatin, with a large number of small chromatophores. The 

 division of the protoplasm into eight take 5 place in the same way as 

 that of the antheridia ; the resulting oospheres are not separated by 

 any membrane of cellulose ; their mode of escape from the oogonium 

 is also the same as that of the antherozoids ; an amoeboid motion was 

 occasionally seen in them ; each invariably contains a nucleus and 

 a nucleolus, as well as a bounding membrane. The application of 

 Zacharias's method, acetic potassium ferrocyanide and iron chloride, 

 showed that the chromatophores, and especially the nucleolus, are rich 

 in albumen, while none could be detected in the rest of the protoplasm. 

 In the actual process of impregnation, the author was unable to 

 detect the formation of particles to determine the direction of the 

 process such as Dodel-Port has observed in Cystosira. The access of 

 the antherozoid could not be followed in living material, but only by 

 bringing a number of oospheres and antherozoids into contact under 

 the cover-glass. The author has no doubt, from the phenomena 

 observed under these circumstances, that the act of fertilization con- 

 sists in the entrance of the antherozoid into the substance of the 

 oosphere. In those oospheres, and those only, which had been in 

 contact with antherozoids, a second nucleus was observed, which 

 could be derived only from the impregnating antherozoid. The two 

 nuclei ultimately coalesce, and the impregnated oosphere then excretes 

 a cellulose-membrane, and begins to divide. 



Formation of Structureless Chalk by Sea-weeds.f — Mr. J. 

 Walther points out that the idea that chalk can only be formed in 



* Ber. Deutsch. Bot. Geeell., iv. (1886) pp. 92-103. 

 f Science, vii. (1880) p. 575. 



