ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 157 



or septa, with separate sexes. The worm lives in a very delicate trans- 

 parent chitinoid tube, to which sand-grains are fixed. 



Swiss Oligochaetes.* — Dr. K. Bretscher has studied the little-known 

 Oligocbaetes of Southern Switzerland, with a view to determining the 

 relation to those found north of the Alps. As yet he has made collec- 

 tions only at Ascona, on the western border of the Maggia delta, but 

 he has found there a number of new species, and an Oligochaete fauna 

 in many ways sharply contrasted with that of Northern Switzerland. 

 The contrast is most marked among the Enchytrajidse ; of nine species, 

 seven are new, two only are identical with northern forms. Among the 

 Lumbriculida), Bichseta sanguinea g. et sp. n., is described. The genus 

 is denned by the characters of the male genital ducts. 



Platyhelminthes. 



Influence of Temperature on Reproduction of Polycelis cornuta.f 

 — Prof. W. Voigt has made an admirably careful study of this problem. 

 In contrast to some easy-going inductions, it is noteworthy that he dealt 

 with over 4000 specimens. The Turbellarian in question is a survival 

 of the glacial fauna, found in many of the mountain streams in Ger- 

 many. Sexual reproduction may occur at any time of year, perhaps 

 with an interruption in midsummer, but it is inhibited locally by a 

 rise in temperature, and seems often all but suppressed. Asexual re- 

 production abounds except in winter. The point is that the worm would 

 have been long since extinct, had it not compensated for the inhibition 

 of sexual reproduction by increased asexual multiplication. 



Nervous System of Distomum hepaticum.; — Dr. J. Havet has used 

 Golgi's method in studying the nervous system of the liver-fluke, and 

 has made out some new points. He finds that bipolar and multipolar 

 nerve-cells occur in large numbers throughout the thickness of the 

 peripheral muscular layer. Their prolongations form extensive intra- 

 muscular and sub-muscular plexuses, which are connected with the 

 adjacent longitudinal nerve-cords. The nerve-cords are made up by 

 the continuations of these prolongations, and by others arising from 

 nerve-cells present in the cords themselves. Similar nerve-cells con- 

 stitute the cerebral ganglia. The " large cells " found in the paren- 

 chyma and in the walls of certain of the organs are for the most part 

 muscle-cells, some are nerve-cells, a few probably gland-cells. All the 

 muscular organs of the body, e.g. genital ducts, the anterior region of 

 the food-canal, the suckers, contain nerve-plexuses, the fibrils ending 

 in the muscles in terminal ramifications with thickened tips. 



Names of Genera of Distomidse.§ — Prof. A. Looss finds that of the 

 genera into which he recently (1899) divided the genus Distomum, no 

 less than nine are preoccupied as genera of insects. He replaces these 

 nine by others, and discusses various debatable cases, in several of 

 which he replaces his genera by others on account of the great similarity 

 between his names and those of existing genera. He also discusses the 



* Rev. Suisse Zool., viii. (1900) pp. 435-58 (1 pi.). 

 ■ t SB. Niederrhein. Ges. Bonn, 1900, I. Halfte, pp. 19-21. 

 \ La Cellule, xvii. (1900) pp. 352-81 (4 pis.). 

 § Zool. Anzeig., xxiii. (1900) pp. 601-8. Cf. this Journal, 1900, pp. 207, 329. 



