ilECENT MEMOIRS ON FRESHWATER RHIZOPODA. ^Ol 



In Cienkowski's form, however, the whole body-mass became 

 directly converted into zoospores, which is very remarkable. 

 May this circumstance, then, be sufficient to distinguish the 

 two forms not only as different species but as separate 

 genera ? 



In the course of from twenty minutes to an hour under 

 the author's eyes the change became completed. During the 

 gradual transformation of the body a modification of the 

 contents was noticeable — originally coarsely granular they 

 became gradually of a mucoso-homogeneous consistence, the 

 nucleus more and more distinct at the same time the pseudo- 

 podia disappeared, the body gradually assumed an ovoid form 

 and the nucleus removed from its central position towards the 

 end, at which were soon noticeable one or two cilia (flagella), 

 by action of which the whole body assumed at first a trem- 

 ulous motion, gradually becoming more vigorous, until at 

 last it passed into a rotation on its longitudinal axis and an 

 advancing movement. The author could not follow out its 

 further fate, these zoospores ever vanished into the "dirt'^ 

 and algse around (as such perverse things will!). The 

 zoospore had an ovoid figure, often appearing drawn out 

 into a stout process ; in some examples the author saw a little 

 posterior contractile space, besides usually a few non-con- 

 tractile vacuoles. 



The near affinity to A. sol was further evidenced by the 

 fission into two of a single individual, and again by the 

 fusion into one of several individuals. If a cluster of such 

 *' conjugating '^ individuals passed into the aoospore state, 

 each lobe of the group, that is each component, previously 

 distinct, individual became a zoospore. Just the same if un- 

 dergoing division, each segment became a zoospore. But 

 further, the zoospores themselves could become "conjugated" 

 or fused together, each portion of the compound body possess- 

 ing its nucleus and cilia, and the whole assuming a roundly 

 triangular figure. Whilst the author could trace results no 

 further, he sees no ground in the fact of fusion as described 

 to base any assumption that it is to be at all regarded as a 

 sexual act. 



Actinosphcerium Eichhornii (Ehrenb.)= Actinophrys sol, 

 Kolliker. 



The structure of this common Heliozoan is now too well 

 known to need any copious description here. Greeff regarded 

 the line of demarcation between the endo- and ectosarc, apart 

 from their difierent transparency, as produced by " a thin 



