Dr. C. F. J. Lachmann on the Organisation of Infusoria. 221 



or the Desmidiacece and Diatomea, cannot certainly yet be 

 regarded as decided. It is well known that a contractile vesicle 

 has not as yet been discovered in them ; their power of motion, 

 their fissiparity, and the discovery by Focke of cilia in the inte- 

 rior of the Closteria"^, cannot settle the dispute. The retractile 

 pseudopodia described by Ehrenberg have not been detected by 

 other observers : the presence of colour in creatures of this 

 group, proved by Ehrenberg, has been supposed capable of ex- 

 planation otherwise than by the eating of coloured particles, as 

 unfortunately the act of feeding was not observed, and the 

 accumulation of colour in particular places, which are then 

 regarded as the nuclei of these unicellular plants, appears to 

 find an analogue in the discovery of Hartigf, that the cell- 

 nuclei of all plants acquire colour more strongly than their other 

 parts. 



A peculiar mode of feeding, which has hitherto always been 

 misunderstood, still remains to be mentioned. It has long been 

 known (since the time of 0. F. Miiller) that other Infusoria often 

 remain adhering to the teutaculiform rays of the Acinetce, which 

 are usually thickened at the extremity ; and that, when they do 

 not soon succeed in freeing themselves, they die. Even O. F. 

 Miiller supposed in consequence that the Acinetce sucked out 

 the contents of these animals, but he says nothing of the mode 

 in which this is effected, and indeed could not observe it with 

 his imperfect instruments. Ehrenberg believed that the cap- 

 tured animals were brought close to a mouth situated between 

 the tufts of rays, and sucked out by this. Stein and Perty de- 

 nied the existence of a mouth in these animals, and grouped 

 them with the Actinophnjdes ; the former, again, distinguished 

 the eating Actinophnjdes (the true species of the genus Actino- 

 phrys, A. Eichhornii and Sol, with difformis, Ehrbg. and oculata, 

 Stein) and those which did not eat (non-pedunculated individuals 

 of Podophrya fixa, and therefore true AcinetinaX). The Infu- 

 soria which come in contact with the rays of the latter are said 

 to die upon them, and then to become dissolved, when the fluid 

 thus produced is taken up by the rays by endosmose. Accord- 

 ing to Perty, the death of the Infusoria is caused by an impale- 

 ment on the extremely fine filaments of the Acineta and ActinO' 

 phrys. Both these ideas were equally paradoxical and incorrect : 

 the true mode of feeding, as may be seen without much difficulty 



* Physiologische Studien, Heft 1. 



t Communicated to the Naturforscherversammlung in Gbttingen, 1854. 



X To these, and indeed to the same genus as Podophrya fixa, belongs 

 the Actinophrys ovata of Weisse, which I have had the opportunity of 

 observing in the neighbourhood of Berlin. 



