ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 187 



Protozoa. 



Reactions of Amoebae. — Asa A. Schaeffer {Biol. Bulletin, 1917, 

 45-72, (; pis.). Amoebai sense beams of light of 20 microns diameter 

 that pass no nearer to them than 100 or 150 microns. In nearly all 

 cases nnder these conditions the amoeba moves directly towards the 

 beam. When the amoeba reaches the beam it either flows over it 

 indifferently, or it reacts negatively to the beam by changing its direction 

 of movement. Beams of spectral light and of white light have approxi- 

 mately the same general efPect. It appears, however, that spectral light 

 at the bine end is somewhat less attractive than that at the red end. 

 Beams of darkness are also sensed at a distance like beams of light, bnt 

 the amoeba usnally avoids them before coming very near them. No 

 explanation is suggested for the sensing of beams of light and of dark- 

 ness at a distance. It is the change of light intensity that determines 

 changes in reactions. Grains of globulin illuminated by perpendicular 

 beams of light seem, on the whole, to be at least as attractive as when 

 not more brightly illuminated than the field. But when globulin 

 grains are laid in dark beams, the amoeba frequently shows unmistakable 

 signs of a tendency to react negatively. An amoeba is positive, negative, 

 or indifferent to beams of light according to circumstances. J. A. T. 



Supplementary Chromatic Body in the Ciliate Maupasella nova. 

 — D. IvEiLiN {Parasitology, 11)20, 12, 92-4, 1 pi.) In this Ciliate 

 parasite of the earth-worm's intestine there is often a ribbon-shaped 

 supplementary chromatic body, of variable position in the endoplasm, 

 and of variable shape. It is different in structure from the macro- 

 nucleus ; there is no continuity between the two bodies ; it does not 

 divide when the macronucleus does. It does not originate from the 

 niicronucleus, nor from abnormal conjugation. In short, it is a very 

 puzzling structure. It may be the result of a condensation of extra- 

 nuclear chromatin, produced by some environmental change. J. A. T. 



Peculiarities of Nicollelidse. — E. Chatton and Ch. Perard 

 {Comptes Rendus Soc. Biol, 1920, 83, 1116-8). In the interesting 

 parasitic Ciliata of this family, found in the food canal of some rodents 

 and Hyraxes, there is a peculiar backward shunting of the mouth, and 

 this is associated with a perturbation of the transverse cleavage. Thus 

 in Golinella ctenodactyli one of the two individuals formed by division is 

 as long as tlie intact individual ; the other is a minute posterior frag- 

 ment. The state of affairs in Nicollela and Pymiothrix is discussed. 



J. A. T. 



Dinoflagellates and other Organisms causing Discoloration of 

 the Sand. — E. Catherine Herdman {Trans. Liverpool Biol. Soc, 1921, 

 35, 1-5, 2 figs.). A study of variable greenish-brown patches on the 

 sandy beach at Port Erin. These were due to various Dinoflagellates 

 and Diatoms. The former were represented by at least three species of 

 Amphidiniiim, and one or more species of Gymnodinium and PolykriTcos. 

 There were also a few unidentified colourless naked Dinoflagellates 

 present. The diatoms were several species of Navimla, Pleurosigma, 

 and other genera, forming brown patches. Small dark green patches 

 were found to be due to species of Oscillatoria. J. A. T. 



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