622 T into er lake. — St arch- Formation in 
been known to be that of a cylindrical coenocyte, having on 
the outside a thick cell-wall, and within this a layer of proto- 
plasm surrounding a large central vacuole. Seen in section 
the protoplasm is clearly bounded on the outside by a plasma- 
membrane and on the inside by a vacuolar membrane of 
similar appearance. Between these two membranes the proto- 
plasm contains the nuclei and pyrenoids and vacuoles of 
various size. There is no indication of any differentiation 
into a layer containing the chlorophyll and one containing 
nuclei. Hydrodictyon contains no differentiated chromato- 
phore. In Chlamydomonas Dangeard has recently sought to 
establish the presence of a distinct chromatophore by the fact 
that the protoplasm of the chromatophore shows an alveolar 
structure, while the surrounding cytoplasm is more like a net- 
work. An examination of Figs. 21 and 26 (PI. XXXIV) 
will show clearly that no such differentiation can be made 
out in Hydrodictyon. The cytoplasm shows no differentiation, 
such as is always observed in Spirogyra cells fixed and stained 
in identically the same way. This agrees with what is 
observed in the living cells of Hydrodictyon , in which, in spite 
of the statement of Klebs and Artari, it is plain that the 
chlorophyll is distributed in the whole peripheral protoplasmic 
layer of the cell. Most striking evidence of the lack of a 
distinct chromatophore is also to be found in the distribution 
of the pyrenoids and nuclei. The pyrenoid, as Schmitz 
pointed out, belongs to that part of the protoplasm that 
contains the chlorophyll, i. e. to the chromatophore where it 
exists as a distinct part of the cell. If, then, there is a distinct 
chromatophore here we should expect to find its position 
indicated by the position of the pyrenoids. On the other 
hand, the nuclei would lie in a layer outside or inside the 
chromatophore. That this is not the case is shown clearly 
in figures where both pyrenoids and nuclei are seen to be 
scattered throughout the protoplasmic layer, neither being 
confined to any one region (Figs. 21 and 26). Moreover, the 
two bodies are often in immediate juxtaposition so that it is 
impossible that one should be considered as in the chromato- 
