FRESH FACTS. 



Geotaxis in Animals. Julia B. Platt. " On the Specific Gravity of 

 Spirostomum, Paramaecium, and the Tadpole in relation to the Problem of 

 Geotaxis," Amer. Naturalist, xxxiii. 1899, pp. 31-38. The tendency that 

 some Infnsorians have to collect near the surface of the water in which they 

 live has been regarded as a reaction to the force of gravity, — a negative geotaxis. 

 To test this Miss Platt has followed Dr. C. B. Davenport's suggestion of alter- 

 ing the density of the fluids. If F. Schwartz was right in his theory of negative 

 geotaxis, the negatively geotactic organism should become positively geotactic in 

 solutions of greater specific gravity than its own, supposing the animal to be 

 normally heavier than water. Miss Platt determined the specific gravity of living 

 Spirostomvm and dead Paramaecium, — both about P017, — but got no positive 

 results in regard to reaction to gravity as far as these Infusorians are concerned. 

 " Small tadpoles that are negatively geotactic do not become positively geotactic 

 when placed in solutions heavier than their own specific gravity, as one would 

 expect were their upward motion in direct response to the action of gravity on 

 the organism as a whole. These tadpoles show constant negative geotaxis in 

 water, in a solution of their own specific gravity, and in heavier solutions." 



Freshwater Protozoa. Robert Lauterborn. " Protozoen-Studien, IV. 

 Theil. Flagellaten aus dem Gebiete des Oberrheins," Zeitschr. wiss. Zool. lxv. 

 1899, pp. 369-391, 2 pis. An impulse to the study of freshwater Protozoa 

 should surely be found in the researches of Dr. Lauterborn, which show how 

 little we know as yet of the numerous beautiful forms inhabiting ponds and lakes 

 and river-beds. In a short time and within a limited area he discovered five 

 new genera of Flagellata. 



Regeneration in Tubifex. H. Haase. " Ueber Regenerationsvorgiinge 

 bei Tubifex rivulomm Lam. mit besonderer Beriicksichtigung des Darmkanals 

 und Nervensystems," Zeitschr. wiss. Zool. lxv. 1898, pp. 211-256, 2 pis. 11 figs. 

 There is less regenerative capacity in Tubifex rivulorum than in many related 

 Annelids. The posterior part is regrown more readily than the anterior end, 

 where in fact never more than three segments are replaced. Except a small 

 most anterior portion the regenerated fore-gut is endodermic, and not ectodermic 

 as in normal development. On the other hand, the hind-gut is regenerated 

 from the ectoderm just as it is formed in the embryo. The regenerated ventral 

 nerve cord arises from an unpaired proliferation, but the supra-oesophageal 

 ganglion has a paired origin which is, however, to begin with ventral in 

 position. 



Parthenogenesis in Stick-Insect. Stadelmann. "Ueber einen Fall 

 von Parthenogenese bei Bacillus rossius F.," SB. Ges. Natur. Freunde Berlin, 

 1898, pp. 153-155. The occurrence of two successive parthenogenetic genera- 

 tions is recorded, thus confirming the previous observations of Dominique, 

 Bolivar, and Krauss. The parthenogenetic ova developed into females only. 



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