ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 339 



to the hsemorrhagic condition of the dentinal fibrils. The changes 

 originate in the odontoblastic cells at the top of the pulp, and work 

 down to the apex followed by distended blood vessels and haemorrhage ; 

 finall)- complete fibroid degeneration takes place. The condition is well 

 shown in the contrasting normal and diseased teeth sections which 

 accompany the communication. J. E. 



C. General. 



Fauna of Ritom Lake. — G. Surbeck {MT. Naturf. Ges. Bern., 

 1917, ix-xi). This lake in Val Piora lies at an elevation of 1831 metres, 

 and is peculiar because of the abundance of sulphuretted hydrogen in 

 the deeper water. This gas is extremely poisonous to the fishes in 

 the lake and forces them to keep near shore and to surface zones of 

 not less than 13 metres in depth. Nevertheless the trout, which show 

 interesting variability and transitions between Salmo lacustris and S. 

 fario, flourish well and attain a large size. They are very fat and 

 the contents of the food-canal show that they feed well on larvte of 

 Plecoptera, Culicidae, and Chironomidae, as well as on Daphnids, 

 Ostracods, and Hydracarina. There are also miller's thumbs {Cottus 

 golio), and not very thriving char {SalveUnus). All the three kinds 

 have been introduced. J. A. T. 



Quantitative Method in Biology. — Julius Macleod (Publications, 

 Univ. Manchester, 1919, 120, xl + 228, 27 figs.). A plea for more 

 measurement. It is necessary to discover the elementary properties or 

 primordia which are significant for an organism — e.g. the number of 

 cells in an organ, the dimensions of the cells, the number of hairs on a 

 particular structure. By convenient methods of measuring these 

 primordia it is possible to determine constants, which are simply the 

 exact expressions of observed facts. The author classifies primordia 

 and illustrates the various methods of measuring them. More measure- 

 ment wall lead to greater precision in specific and generic diagnosis, 

 increased security in taxonomy, and deeper recognition of variability, 

 modifiability, growth-stages, and gradation axes. A species is regarded 

 as marked by its chemical individuality, which separates it from all 

 others. Species arise not by continuous transformation, but by 

 mutations due, directly or indirectly, to novel conditions of life. 



J. A. T. 



Resistance of Red Blood Corpuscles to Hypotonic Salt Solu- 

 tions. — Matsuziro Takenouchi (Anat. Record, 1919, 17, 4:5-.37, 

 1 chart). The resistance of the erythrocytes of albino rats at different 

 ages to hypotonic salt solutions is related to the water content of the 

 serum normally surrounding the corpuscles. The concentration of the 

 salt solution causing haemolysis increases with age. The concentration 

 of the hypotonic salt solution which causes approximately 20 p.c. 

 hemolysis is 0-441 p.c. for the youngest, and 0'170 p.c. for the oldest 

 age group. The erythrocytes of the female are less resistant — i.e. 

 respond to a higher concentration of the hypotonic salt solution than 

 do those of the male. J. A. T. 



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