794 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



sion in a weak solution of sodium chloride causes immediate suspension 

 of the movement, which commences again on immersion in pure water ; 

 from which he concludes that it is not the result of osmotic processes. 

 The interior protoplasm appears to have a tension of 4-5 atmospheres, 

 which would cause it to rush out through the openings in the valve, if 

 tbe channels which lead to these openings were not of a winding and 

 complicated character. He believes rather that the movement itself and 

 the direction of this movement are the result of motor forces which 

 are manifested on the surface, residing in the protoplasm which is pro- 

 truded through the raphe. 



Auxospore of Terpsinoe.* — Herr O. Miiller describes the auxospore 

 of Terpsinoe musica from St. Domingo. The length of the valve of the 

 auxospore varies between 223 and 257 ya, while that of the mother-cell is 

 only from 92 to 106 /x. The formation takes place on the same general 

 plan as that of Melosira, and is a process of simple rejuvenescence rather 

 than of sexual reproduction. The mass of protoplasm which expands 

 and projects between the valves of the mother-cell tills up the older half 

 of this cell, withdrawing itself entirely from the younger half; the 

 perizone surrounding the portion of the protoplast which adheres to 

 the older half. The new girdle is formed in the portion of the proto- 

 plasm surrounded by the perizone which faces the younger half, and 

 this is followed by the excretion of the second auxospore-valve. In 

 Ihe genus Terpsinoe the cavity of the valves is divided by septa, the 

 purpose of which is to bring the chromatophores into a profile-position 

 under the powerful tropical insolation. 



Diatom-beds of the Yellowstone.! — Mr. W. H. Weed describes the 

 composition of the enormous diatom-marshes and diatom-beds of the 

 Yellowstone National Park, U.S. He finds them to consist mainly of 

 the following species : — Denticula valida and elegans, Navicula major 

 and viridis, EpitJiemia arrjus and var. ampliicepJiala and E. Hyndmannii, 

 Cocconema cymhiforme, Achnanthes gihherula, Mastigloia Smithii, and 

 Fragillaria sp., of which the first is the most abundant. 



/3. Sdiizomycetes. 



Micro-organisms and their Destruction.! — Dr. A. B. Griffiths, who 

 has continued his researches on micro-organisms, thinks that as the 

 microbes, which are the real cause of certain contagious diseases, may be 

 destroyed by various germicides, -we ought, by further investigation, to 

 discover remedies for such scourges as consumption and syphilis. The 

 author finds that the vitality of Bacillus tuberculosis is considerable, and 

 that it is capable of being dried up in the atmosphere for many weeks 

 without its vitality being impaired. The electric current destroys the 

 vitality of certain microbes. Dr. Griffiths has discovered that a new 

 microbe, which he calls Bacterium allium, is the cause of putrefaction in 

 the onion, and that it liberates small quantities of sulphuretted hydrogen. 

 The soluble zymoses secreted by living microbes are capable of being 

 destroyed by germicidal agents, and are thus rendered incapable of pro- 

 ducing cLemico-pathological changes in the blood-tissues. 



* Ber. Deutseh. Bot. Gesell., vii. (1889) pp. 181-3 (1 pi.)- 



t Bot. Gazette, xiv. (1889) pp. 117-20. 



% Proc. R. Soc. Ediub., xv. (1888-9) pp. 33-65. 



