M. N. Lieberkuhn on the Anatomy of the Infusoria. 323 



The nucleolus has very different characters in all the specimens 

 of Bursaria flava I have hitherto observed. It was always so 

 small that it was difficult to find it, and never became visible 

 until the Infusorium was compressed, while in Ophryoglena flavi- 

 cans it may usually be seen through the integuments. Its form 

 is globular, and it presents no structure. It generally adheres 

 firmly to the surface of the ovate nucleus. 



The nucleus is not any larger in the rather larger specimens 

 of Bursaria flava which possess two contractile vesicles. I 

 met with some of them occasionally in company with the one- 

 vesicled. They did not difi^er from the rest at all in shape, in 

 the condition of the ciliary clothing, or in the formation of the 

 mouth, so that I held them to be identical until I observed the 

 second contractile vesicle, or the somewhat differently formed 

 and smaller watch-glass-shaped organ ; which last, in the 

 specimens I have hitherto examined in respect to this point, had 

 not a circular, but an elliptical base, — so far at least as a judg- 

 ment can be formed from the mere aspect. Measurements 

 made on one specimen gave — length of the animalcule, y^gths of 

 a millimetre ; greatest thickness, y%ths of a mill. ; diameter of 

 the globular nucleus, y^^ths of a mill. ; of the nucleolus, y^^'^^ths 

 of a mill. ; distance of the mouth from the head-point, y'^y^^ths 

 of a mill. ; distance of the contractile vesicles apart, y^jth of a 

 mill. ; of the hinder one from the tail-point, yj^ths of a mill. ; 

 greatest diameter of the base of the watch-glass-shaped organ, 

 yo^'^^ths — smallest, y^^^^ths of a millimetre. 



The Vascular System, ^ 



This consists of two contractile vesicles, and a system of canals 

 which open into them. The best subjects for the examination 

 of these objects are usually found in those specimens of Bursaria 

 flava which contain in their interior only the smallest forms of 

 the strongly refractive granules. I frequently found such among 

 the others in the pools of the Berlin Thiergarten. The con- 

 tractile vesicles lie in the immediate vicinity of the mouth, a 

 little behind it : if we conceive the animalcule to lie upon 

 its back, with the mouth upwards and the end of the head 

 turned away from the observer, the contractile vesicle will 

 be placed to the left of the mouth, on its convex side, distant 

 from it about a quarter of a circumference; when there are 

 two vesicles, the anterior contractile vesicle lies exactly in the 

 same spot, and the posterior is cut by a straight line drawn from 

 the anterior vesicle to the tail- point. The position is just the 

 same in the Ophryoglence above described. If we examine a 

 Bursaria of this kind with a power of about 300 diameters, we 



21* 



