ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 435- 



Uses of Diatoms.* — M. Lanzi considers the diatoms from a bio- 

 logical point of view, and mentions some of the uses to which they may 

 be put. Besides the function which they exercise in common with 

 other algae — that of assimilating nitrogen in one form or another — they 

 help to form food for certain animals in both salt and fresh water. 

 They are found in Peruvian and other guanos, showing that they have 

 been devoured by birds ; and in certain parts of the world, notably, on 

 the shores of the Orinoco and in Italy, a fossil flour containing diatoms 

 is used as food by the human inhabitants. The paper closes with two 

 lists of thirty-two and fifty-two species found in the stomach and 

 intestines of two fish, Leuciscus muticellus and Chrysophrys auratir 

 respectively. Diatoms are also employed as objects for testing the 

 powers of definition of a Microscope lens. 



Transmutation of Various Stages in Diatomacese.f — C. Meresch- 

 kowsky continues his explanation of the law which governs the forms 

 of certain diatoms. As stated in the account of the first part of his 

 paper, he calls it the law of translation of stages in Diatoms. In this r 

 the concluding part, he gives several instances of genera and species 

 Avhich show certain markings hitherto not to be explained, but easily 

 accounted for if the existence of his law be granted. The longitudinal 

 sinus or fissure in the plaque of Pyrenophoreas is thus the crystallisation^ 

 so to speak, into a permanent form, of an otherwise passing stage of 

 development. The same explanation holds good for Catenula, Neidiinx 

 and certain species of Nitzschia, for example, N. angular is and var. 

 ({(finis, and N. distans. In the same way transverse fissures are seen in 

 species which divide transversely, as Navicula digitoradiata, and certain 

 species of Gyrosigma and Caloneis. This law does not explain, however,, 

 such transverse fissures as those of Cymbella, Rhoicosphenia, etc., which 

 divide longitudinally. The author gives other instances of peculiarities 

 which may be explained by his law, and suggests that not only specie* 

 but also genera may have originated in a short time from the arresting 

 of certain stages in the development of a species. He thinks that the 

 same law may possibly hold good among Hydroids, Crustaceans, Infu- 

 soria, and even Fungi. 



Alga Related to Raphidium polymorphum.J — M. G. Raymond! 

 describes the life-history of an alga from the pools in clay soil at 

 Trappes in France. It is closely analogous to Raphidium polymorphum . 

 It lives at the bottom of shallow pools fed by rain-water, and cultures 

 of it are destroyed by the addition of calcareous water. It possesses- 

 but slight mobility, and strong sunlight destroys cultures of it in a 

 short time. The gametes appear after the cessation of the severe cold ; 

 the zygotes, which result from copulation, sink to the bottom and give 

 rise to : (1) A first generation of zoospores, which form large zoo- 

 sporangia, from which issue, as a rule, four new zoospores. (2) The 

 zoospores of the second generation reproduce themselves by transverse 

 division. (3) This third generation gives rise to the gametosporangia, 



* Att. Pont. Accad. Rom. Nuov. Lincei, lvi. (1903) pp. 129-41. 

 t Journ. de Bot, xviii. (1904) pp. 76-83 (3 figs, in text). 

 % Miorogiarhc preparateur, xii. (1904) pp. 11-19. 



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