Hydrodictyon utriculatum . 6 23 
phore and the other not (Fig. 27). Still another point of 
importance is the fact that in those cells containing an 
abundance of starch, practically the whole layer of proto- 
plasm, from the plasma- membrane on the outside to the 
vacuolar membrane on the inside, is filled with the starch- 
grains, all of which, as I shall show below, have their origin 
in the pyrenoid, and are later transferred bodily to other 
parts of the cell (Fig. 26). If we are to think of a differentiated 
chromatophore we should expect the starch to be retained 
within its body, as is clearly the case, for example, in Spirogyra. 
It would seem that, then, Hydrodictyon is to be placed among 
those plants in which the chlorophyll is distributed generally 
in the cytoplasmic part of the protoplast. Klebs and Artari 1 
have described a chromatophore in Hydrodictyon made up 
of a complicated network, which may, according to Artari, 
become a single slightly alveolar layer, or, according to Klebs, 
become divided into several layers having a net-like structure. 
Both of these observers worked, however, with surface-views 
of the cells, a condition under which accurate observation of 
the whole protoplast is quite impossible. The numerous 
vacuoles which frequently appear in the cells might easily 
lead to some such interpretation as that of Klebs or Artari, 
provided only surface-views were had. 
It is an interesting question whether the condition above 
described for Hydrodictyon is a primitive condition in chroma- 
tophore-development. Prior to the appearance of Schmitz’s 
work on the chromatophores of the Algae, it was not un- 
common to have forms described as having the chlorophyll 
diffused throughout the cytoplasm. Schmitz first insisted 
upon the doctrine that the chromatophore in all Algae was 
a distinct cell-organ, and that there was no such thing as 
chlorophyll contained in undifferentiated cytoplasm. This 
doctrine of Schmitz was soon extended to all of the so-called 
plastids by Schimper, and is now the prevailing theory among 
botanists. Still it is not impossible that a more careful 
investigation of a large number of forms will reveal conditions 
1 Zur Entwickelungsgeschichte des Wassernetzes. Moskau, 1890. 
