246 Dr Wagner on the Structure and ■ 



day, the 4th November, the number of the animalcules had in- 

 creased, as well as that of the empty sacks adhering to the sides 

 of the glass. A number of new eggs had also been laid, which 

 were chiefly collected towards the surface of the water. A glass 

 with a magnifying power of three, distinctly shewed, in the 

 grown animals, a nearly ripe ovum ; others were destitute of the 

 round dark point beside the intestinal canal ; these had probably 

 a short time before evacuated their ova. Besides the Hydatina, 

 there were many still smaller infusoria, which swam about with 

 much vigour, and appeared, under the microscope, like the 

 Vorticella larva^ Miiller ; their eggs seemed to be much smaller 

 and more spherical, interspersed among the larger ova. On the 

 5th November, still more eggs had been laid, and new animals 

 excluded ; the numbers of the Vorticella larva had much dimi- 

 nished. On the 6th, many more animals seemed to have been 

 excluded, but no new eggs had been laid. The Vort. larva had 

 almost entirely disappeared from the infusion. On the 8th, the 

 number of animalcules remaining was comparatively small. It 

 continued nearly stationary to the 11th, on which day no new 

 eggs were found on the sides of the vessel, although the dark 

 spot (ovarium) beside the intestinal canal, was very distinct. 

 On the 20th November very few individuals remained, and no 

 new eggs had been laid. 



With regard to the size of the animal, my observations are 

 not quite in accordance with those of Ehrenberg. In his table, 

 he states it at from Y' ^^ V- I usually found them larger ; 

 the largest individuals were very commonly ^'", some almost 

 y\ more exactly /g'". The ova could be detected with the 

 naked eye, when the glass was held up to the light, like small 

 dark points adhering to its sides ; and my eye is capable of dis- 

 tinguishing objects of the size of ^^"','vfhen close to the eye, 

 and in active motion like the infusoria. With a lens magnify- 

 ing three times, the eggs appeared like small disks, and the 

 empty sacks could be distinctly perceived adhering to the sides 

 of the glass. Under the microscope, their sizes varied from 

 A'" to ^^"\ without, however, their magnitude appearing to 

 depend upon their internal development ; for I found ripe em- 

 bryos both in the small and large ova. Their form was gene- 

 rally oval, approaching more or less to a circle. Their colour 

 was often dark, yellowish-brown, and opaque ; some were par- 



