ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 293 



them develop in various solutions, such as potassium bichromate 3 p.c, 

 double streno^th Gram's iodine solution, thymol water, etc. The early 

 stage and the completely developed cyst of Coccidium cuniculi, found in 

 the Philippine rabbits, is figured (figs. 4 and 5) for comparison with the 

 Isospora cyst. J. E. 



Mutation in Bacteria. — L. Doncaster (Froc. Camb. Phil. Soe., 

 19, 5, 269). It was noticed that the recorded ratio of occurrence in 

 oases of meningitis of the four agglutination-types of meningococcus 

 •corresponded very closely with the ratio of occurrence of the four iso- 

 agglutinin groups of blood in a normal human population. It seemed 

 possible, therefore, that by growing meningococcus of one type in media 

 containing human blood of different groups, mutation to other types 

 might be induced. Experiment showed that considerable differences in 

 type of agglutination resulted, but it was concluded that this was caused 

 by the sorting out of races of different agglutinability from a mass 

 culture rather than by true mutation. 



Philippine Economic Plant Diseases. — Otto A. Reinking 

 {Philippine Journ. Sci., Sect. A, 1918, 13, 217-74, 22 pis.). The author 

 enumerates and summarizes the plant diseases encountered in the 

 Philippines, giving the bacterium or fungus responsible for each con- 

 dition. The monograph is illustrated with plates of diseased plants and 

 woodcuts of vegetable sections, and diagrams of the responsible micro- 

 organisms. J. E. 



■■n'- 



All Dead Bacteria are not Ag-positive. — Axel Cedercreutz 

 {Arlciv. for Lire 3Iedicin, 1919, 51, 269-81). Aage Nyfeldt in June, 

 1907, published investigations which led him to conclude that all dead 

 organisms are Ag-positive, while all living — i.e. living previous to 

 fixation — are Ag-negative. Cedercreutz, however, considers that no 

 staining method has yet been perfected whereby dead and living bacteria 

 may be distinguished. In bacteria life and staining power are not 

 always correlated. In 1900, whilst studying a pleomorphic skin coccus 

 (resembling the gonococcus, but Gram-positive), the author observed 

 that several forms, though dead and unable to reproduce, stained well 

 with polychrome methylen-blue. The above forms grow in cultures 

 made on 5 p.c. dextrose-agar. The bacterial varieties retain their 

 staining properties even after killing by heating ten to fifteen days. 

 In these, and in even older dextrose-agar cultures (when the organisms 

 •can only be separated by the addition of sterile water) the bacteria 

 «tain quite as well as those in a young culture. Although the cocci 

 of the fifteen-day dextrose-agar culture are dead, they seem to acquire 

 on this medium a power of " conservation," so that even after killing 

 they retain both their form and their staining properties. Following 

 Nyfeldt's article, the author tried the effect of silver impregnation 

 on these " conserved " bacteria, using the methods suggested by 

 Nyfeldt, with the result that the majority of the cocci were Ag- 

 negative. Although in some cases isolated Ag-positive cocci were 

 found, these the author concluded had become impregnated with the 

 dextrose-agar, which is in itself Ag-positive. The greater number of 



