399 
more shallow than are those of the chloroplast. If an optical 
section of the peach endocarp could be obtained, the ridges which 
surround the depressions would, to a certain extent, produce the 
delicate, bar-like projections as on the margins of the chloroplasts. 
My attempts to make drawings of these surface-appearances 
have failed, although I have had the assistance of beautiful photo- 
micrographs prepared for me by Dr. H. G. Piffard, of New York, 
a most accomplished photo-micrographer. The structure is so 
delicate and so minute that even the photo-micrographs repro- 
duced by the half-tone process would not satisfactorily show it. 
To see it with the microscope certain conditions are required. 
These conditions must be complied with, or the depressions, 
as I believe them to be, will appear as whitish elevations com- 
Parable to the “pearls” on the diatoms when these plants are 
resolved in the common, that is, the incorrect way. These chro- 
matophore-pearls, like the diatom-pearls in certain cases, become 
black depressions when the objective is properly focussed. If the 
apparent elevations on-certain parts of certain diatoms are not 
elevations, then the apparent pearls as seen with a certain focus 
On the chromatophores are not elevations. In both cases they 
must be depressions or apertures; otherwise the entire fabric of 
the secondary structure of the diatoms falls to the ground. If the 
Surface of the chromatophores of Astrophyllum sylvaticum is not 
deeply pitted, and if the entire structure, as seen in optical sec- 
Hons, is not similar to the trabecular formation of the ordinary 
Ssponge-skeleton, then those of us that have taken pleasure in the 
Study of the secondary structure of the diatoms have had all our 
Work for nothing, and have been pursuing aphantom. But the ex- 
stence of this secondary diatom-structure can be demonstated 
yond a peradventure. 
The lowering of the objective to obtain this “ black-dot” reso- 
lution gradually brings into view the blackness of the depressions, 
With the well-defined outlines of the narrow elevations which sur- | 
‘ound them. The surface of the chromatophore then has a spongy 
4ppearance, the black spaces between the irregular network seem- 
‘ng to enter the substance of the chloroplast and there to produce , 
not a structureless, homogeneous body, but a body of green 
™eshes. Those that have studied the secondary structure of cer- — 
