Dr. A. Gr iiber on Protozoa. 321 







III. On Processes of Fusion in Actinophrys sol *. 



It is well known, as a phenomenon frequently observed and 

 described, that an intimate union of two or more individuals 

 occurs among the lleliozoa. In this way regular syncytia 

 may be produced, often consisting of more than twenty indi- 

 viduals. As regards the signification of this process, it 

 appears to be certain that it stands in no relation to repro- 

 duction. The lleliozoa usually separate again without our 

 being able to observe any alteration either in the nucleus or 

 in the soft body. Hence it has been supposed that the sole 

 purpose of these unions was to facilitate the reception of food, 

 in favour of which Ave have also the circumstance that in this 

 state the lleliozoa generally contain much nutritive material. 



I have long had it in view to go carefully into this ques- 

 tion, but could never obtain sufficient material. In this I 

 only succeeded quite recently, when an abundance of Actino- 

 phrys sol had become developed in a small aquarium of the 

 Institute here. Nevertheless I found it impossible to throw 

 any more light by my investigations upon the significance of 

 the colony-formation among the Heliozoa. But some other 

 remarkable processes came under my observation, upon which 

 I may report briefly. These are phenomena of fusion in 

 which, in contrast to the formation of colonies, the two parts 

 passed completely into each other (that is to say, one of them, 

 namely the smaller one, was devoured by the other), and from 

 which it appeared that separated fragments of Actinophrys or 

 small individuals without a nucleus are able to perform their 

 normal functions. 



A full-grown normally formed Actinophrys sol had ap- 

 proached a much smaller specimen furnished with only a few 

 pseudopodia, had been suddenly attacked by it, and in a short 

 time passed entirely into it. After the union had become 

 complete, so that the larger Actinophrys had again assumed 

 its rounded form, I killed it with chromic acid, stained it with 

 carmine, and mounted it in Canada balsam, when it appeared 

 that only a single nucleus was to be seen in the centre of the 

 Heliozoan. Hence I thought it must be supposed that the 

 nuclei as well as the protoplasmic bodies of the two indivi- 

 duals had passed into each other. 



To arrive at a certainty upon this point I endeavoured to 

 observe the process again ; and by shifting the covering-glass 

 and drawing off and adding water under it, I succeeded in 



* The essential parts of the following results have already been pub- 

 lished in the ' Zoolo^ische Anzeiger/ no. 118. 



