ZOOLOGY AND BOTANY, MICROSCOPY, ETC. Ill 



a parietal disc with a starch-grain. The zoospores are formed by 

 repeated bipartition, and escape through an opening in the outgrowth 

 by which the parasite is attached to the host ; they are pear-shaped 

 and biciliated. Larger zoospores, with four cilia, have also been 

 observed by Lagerheim, but no conjugation of these with the micro- 

 zoospores has yet been detected, as in the case of C. Lemnce. Both 

 kinds appear to be capable of direct germination. 



Fronds of Laminariacese.* — In the 4th part of his ' Observationes 

 Phycologicae,' Prof. J. E. Areschoug describes the 11 species of 

 Scandinavian Laminariaceas. Nereocystis LuetJceana and Pelagophycus 

 giganteus are annual, the plant dying entirely every year. In the 

 perennial species the new fronds begin to show themselves in January, 

 and attain their complete development towards ApriL In Laminaria 

 flexicaulis the old frond begins to bear spores at the moment when the 

 new frond appears, and dies in the middle of the summer when the 

 new frond has become large. In Alaria esculenta all the fronds 

 disappear in the autumn before the new fronds have made their 

 appearance, but the stem is perennial, and produces new fronds in 

 the spring. 



Motion of Diatoms.f — Mr. C. Ouderdonk, having studied the 

 Diatomacese for some time, mainly in regard to a discovery of their 

 mode of motion, has come to the conclusion that there is a fluid in 

 motion on the outer surface of the valves, no other supposition 

 accounting for the observed phenomena. He therefore endeavoured 

 to find the fluid, or semi-fluid, and thus describes his results :-^ 



" I turned my attention to the Palmellaceae. Here I had an in- 

 visible frond, firm enough to be lifted out of the water and hold 

 the green globular masses contained in it. I began to search for 

 stains to make this invisible matter visible. I found that methyl- 

 aniiin-green stained the Palmella a clear blue, while it also hardened 

 it. I found that this stain also stained the living diatoms blue ; more 

 than this, my success was far beyond what I had hoped, for I saw 

 in many cases a blue mantle slowly unfold and detach itself from 

 the now white denuded frustule. Subsequently, by many observa- 

 tions, I found that all diatoms which have come under my notice are 

 encased in a gelatinous pallium ; that this pallium is most manifest 

 under the action of the stain in the case of the diatoms with strong 

 motion, and least manifest in the case of fixed diatoms like those 

 with a stipes ; that the Diatomaceae have not internal motion analogous 

 to the motion called cyclosis in the Desmidiefe ; that the motion on 

 the outside of the outer covering of the Diatomaceae is strongly 

 analogous to the motion on the inside of the outer covering of the 

 Desmidieas. 



" From the above-mentioned facts, and others which time forbids to 

 mention, I offer as a theory that the motion of the Diatomaceaa is 

 caused by what I will call external cyclosis. I do not court credence 



* Acta Keg. Soc. Sclent. Upsalensis, iii. (1884) 16 pp. See Bull. Soc. Bot. 

 France, xxxii. (1885). Rev. Bibl., p. 180. 

 t The Microscope, v. (1885) pp. 205-6. 



