440 
daß ich bereits so frei war, den Irrthum bezüglich der vermeintlichen 
Umwandlung von Hydra grisea in viridis selbst zu corrigiren. 
Übrigens kann ich den Zweifel auch jetzt noch nicht unter- 
drücken, ob Herr Dr. Otto Hamann und ich wirklich dasselbe Ob- 
ject beobachtet haben. Schon in seinen früheren Arbeiten spricht Herr 
Dr. Otto Hamann von »jodhaltigen gelben Zellenc: ich habe 
meinerseits »jodhaltige« Zellen niemals beobachten können, außer wenn 
ich selbst Jod unter das Deckglas fließen ließ, um die gelben Zellen 
auf Stärke-Reaction zu prüfen. 
2. Contributions to the Cell-Theory. 
By Patrick Geddes. 
I. A Theory of the Life-History of the Cell. 
Our current conceptions of the groups of the Protozoa are apt to 
be based upon their most prominent and permanent characters only. 
One thinks of an Infusorian as a ciliated or flagellated organism of 
permanent form, of a Radiolarian as a highly differentiated Rhizopod, 
with two layers of protoplasm, a gelatinous envelope, and a siliceous 
skeleton, while in description of a Heliozoon special attention is paid 
to the radiating pseudopodia with their axial filaments. In lower forms, 
however, more attention is paid to the whole life-cycle. In the Amoeba 
the encysted state is almost as familiar as the active, in the Gregarine 
sometimes more so, while in such a remarkable Moneron as the Proto- 
myxa of Heckel it is hard to say whether the encysted, the amoeboid, 
the flagellate or the plasmodial is the most prominent stage. For here 
is no single permanent highly differentiated form, but an eventful life- 
history in which one protean mass of protoplasm passes through a cycle 
of at least four distinct phases. 
Such discoveries as those of the life-history of Monads, of the 
ciliate embryo of Acinetae, of the multiplication of Radiolarians by Zoo- 
spores or of the union of several Actinosphaeria or Gregarines into a 
plasmodium point in the same direction, — in fact the whole progress 
of recent research has largely lain in revealing the existence in even the 
most highly differentiated forms, of a life cycle almost as complete as 
that of Protomyza. 
In other words if we make a diagram of Protomyzxa, exhibiting the 
encysted , the ciliated, the amoeboid and the plasmodial stages, an 
essentially similar life history may be sketched out for all the higher 
groups of Protozoa, with blanks it is true, but blanks which the pro- 
gress of discovery is constantly diminishing and seems likely indeed 
