( 245 ) c.ii^ 



Observations upon the Structure and Development of the htfu- 

 soria. By Dr Rudolph Wagner of Erlangen. 



X HE following observations were made in the summer of 1831, 

 and I have to regret that the microscope which was employed 

 cannot be compared with that by means of which Professor 

 Ehrenbcrg of Berlin was enabled to make his masterly researches 

 into this department of nature. The instrument employed was 

 good, but of the old construction. The object-lenses were ma- 

 nufactured by Utzschneider and Frauenhofer; and, although 

 their defining power was excellent, they did not magnify more 

 than from forty-eight to sixty diameters. 



I. Development of the Hydaiina Senta *. 

 The Hydatma Senta is not unfrequently found in the neigh- 

 bourhood of Erlangen, in pools and marshes, the surface of 

 which is covered with duck- weed, but it is not common in these 

 situations, being more frequently obtained by keeping water 

 enclosed in covered glasses in the house for some days after the 

 successive production and disappearance of other infusorial 

 forms. This was the case with a natural infusion in which I de- 

 tected, on the 3d November, a tolerable number of the Hydatina, 

 These were of all sizes ; some were visible to the naked eye, 

 but still more distinctly with a common pocket lens. Some of 

 the animals swam about in the water, but the greater number 

 attached themselves by their posterior extremity to the walls of 

 the vessel and vibrated freely the anterior part of their bodies, 

 in all directions, in the fluid. On the sides of the glass, and 

 still more abundantly towards the surface of the water, was a 

 brownish pulverulent mass, interspersed with small globular 

 greenish grains, — the dead bodies of the Eugiena viridis, Ehren- 

 berg. When a portion of this mass was placed under the field 

 of the microscope, I observed a number of darker coloured and 

 more distinctly defined oval or rounded bodies, which I imme- 

 diately recognised to be ova, and there was visible besides a 

 number of empty sacks, split up the middle, which had evi- 

 dently been the envelopes of former ova. On the following 

 • Figures illustrative of the external form and internal structure of the 

 Hydatina senta are given in PL IV. of the preceding volume of this Journal. 



