ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 239 



Ripening of Backstein Cheese.* — Herr O. Laxa found in two kinds 

 of Backstein cheese various microbes, among which an Oidium, lactic 

 acid bacteria, Saccharomycetes, and four bacilli were constantly present. 

 In the cheeses examined, symbiotic aud metabiotic processes took place, 

 and these had a direct influence on the aroma of the cheese. The Oidium 

 was found to consume a part of the free acid, and in this way prepared 

 the ground for other microbes. It was also responsible for the produc- 

 tion of the intense aroma of the slimy portions of the cheese. The 

 power of peptonising casein was found to be possessed, not only by cer- 

 tain species, but this power could be exerted by the symbiotic action of 

 microbes which individually could liquefy casein only with difficulty. 

 The aroma of the lardaceous portions of the cheeses examined was found 

 to be a product of the symbiotic action of different microbes. 



Though a short description of the various microbes isolated is given, 

 a more detailed account, with special reference to their share in the 

 ripening, is promised later. 



Myxomycetes. 



Myxomycetes as the exciting cause of Tumours in Animals.f — la 

 a preliminary report, Prof. W. Podwyssotzki communicates the results 

 of experiments on guinea-pigs and rabbits, which were inoculated with 

 Pla8modiophora Brassicse. In 15-18 days after inoculation, tumours 

 appeared, and these on microscopical examination were found to present 

 the appearances of sarcoma or endothelioma or granuloma. Within 

 the tumour-cells spores of tbe parasite were frequent. The spores excite 

 a nuclear proliferation, aud a metamorphosis of the nuclear substance. 

 Giant-cells were not uncommon, but, though surrounded by spores, did 

 not contain any. The tumour-cells are, as seen in sections, much vacuo- 

 lated, and appear to be filled with fat-globules. 



Plasmodiophora Brassicse. J — Dr. S. Nawaschin records a series of 

 observations on the minute structure of this parasite, and on the changes 

 which it undergoes during its iutercellular life. It presents the pheno- 

 menon which he terms dimorphism of the nucleus. In the amoeba-stage 

 it exhibits a decidedly abnormal kind of indirect division ; while in the 

 spore-forming plasmode the division of the nucleus is of a typically 

 karyokinetic character. 



The differentiated group of infected parenchymatous cells of the 

 host, the seat of the root-swelling, arise by repeated division of the 

 cells first infected. In the course of the growth of this swelling there 

 arise in the infected cells a number of multinucleated amoebae which 

 do not at first coalesce into a plasmode. The formation of the plasmode 

 is preceded by characteristic changes in the structure of the amoebaa 

 and in their nuclei. It takes place only after the complete exhaustion 

 of the nutrient cell. In the mature plasmode the spore-formation is 

 prepared for by repeated mitotic division of the nuclei. During the 

 vegetative period of its development the parasite does not kill the 

 nutrient cell, but simply causes hypertrophy. 



* Centralbl. Bakt. u. Par.. 2" Abt., v. (1899; pp. 755-62. 

 t Op. cit., 1" Abt., sxvii. (1900) pp. 97-101. 

 \ Flora, lxxxvi. (1899) pp. 404-27 (1 pi.). 



