G56 



Außer dieser Rinne ist der ganze Rücken mit zahlreichen runden 

 Grübchen und nach der Mitte zu gekrümmten kurzen, glatten Borsten 

 versehen. — Ventral: Sternalschild sehr lang, mit zahlreichen großen 

 runden Grübchen. Ventrianalschild kurz; ventraler Teil desselben 

 mit ebensolchen Grübchen. Ventrianal-, Metapodial- und Peritre- 

 matalschilder mit hervorspringenden, dicken, chitinösen Rändern. — 

 Hypostoma und erstes freies Palpenglied (Trochanter) mit je einem 

 dreizähnigen Haar. 



Oslebshausen, unter Steinen bei der kl. Brücke über die »alte« 

 Weser (1 Deuton.) 11. IV. Ol. 



Gen. JEremaeus C. L. Koch. 

 18. E. varius Oudms. et Vgts. n. nom. 

 Diese Art wurde schon 5. Sept. 1900 von Oudemans unter- 

 schieden (Tijdschr. voor Entom. v. 43, p. 162), jedoch nur als eine 

 Aberration oder Varietät angesehen. Sie gleicht E. exilis (Nie), hat 

 aber keine Lamellarspitzen. 



9. A Method of Demonstrating the external Discharge of the contractile 



Vacuole. 



By H. S. Jennings. 



(With 1 fig.) 



eingeg. 3. Mai 1904. 



Penard (Faune Rhizopodique du Bassin du Léman, Geneva, 

 1902, p. 644 — 662) has recently opened again the question whether 

 the contractile vacuole of Protozoa really discharges to the outside, 

 pointing out that the evidence on which this generally received view is 

 based is very inadequate. A method by which the external discharge, 

 when it occurs, can be demonstrated experimentally is then desirable. 

 In studying the currents produced by the cilia in Paramecium.^ I came 

 upon such a method, by which it is possible to demonstrate with the 

 greatest ease that in this organism and various others the contents of 

 the contractile vacuoles are discharged to the outside. The method 

 is extremely simple. It consists in mingling a large quantity of finely 

 ground India ink, or Chinese ink, with the water containing the ani- 

 mals. The ink is procured in sticks, in the usual way, and is rubbed 

 up with two or three drops of water in a watch glass till the water is 

 thick and muddy with the finely ground ink. In this the Paramecia 

 are mounted and covered in the usual way. The layer of water must 

 be thin, so that the animals shall not be completely hidden by the ink. 

 When such a preparation is placed on the stage of the microscope, 

 and much light is admitted from below, it is black and nearly opaque. 



