Olive, Mitotic division of tlie iraclei of tlie Cyanopliyceae. 
13 
tlie Botanical Grarden of Harvard University, and tlie otlier 
species from tlie Botanical Grarden of tlie University of Bonn; 
or from ponds in tlie neigliborliood of Bonn. Five species of 
Oscillatoria , and one species eacli of Phormidium, Calothrix , 
Nostoc, Gloeocapsa, and Cylindrospermum, liave been studied. 
But two metbods of fixation liave been generally eniployed: 
viz., Flemming’s weaker solution, and Strasburger's modi- 
fication of Flemming’s niixture, sometimes called tke „middle 
solution 0 . Tlie SCk-alcokol niixture, recommended by He gl er, 
gives, as lie asserts, a skarply marked central body, but I liave 
found tkat tke nuclei so treated are unnaturally slirunken, and 
tkat tke wkole cell is frequently plasmokzed (see figs. 2, 3), 
kence I early abandoned tliis metkod. After fixation, tlie masses 
of filaments were wasked for a few liours in water, tlien deky- 
drated by passing tlirougk tke usual grades of alcoliols. Tkey 
were tlien carried tlirougk cliloroform or xylol, successively 
infiltrated witli paraffine melting at 52 0 and 60 °, and finally 
sectioned 1 — 4 y tkick. Tke muck eniployed stains, Flemming’s 
safranin, gentian violet, witli or witkout orange Gr, and Heiden - 
liain’s iron kaematoxykn, sometimes followed by eosin or orange, 
gave rnost excellent results. For certain purposes, a mixture of 
metkyl blue and eosin, or of metkylene blue and eosin, was 
used; and a few otlier stains were tried, but none were so 
satisfactory for tke nuclear elements as tke two Standard stains 
mentioned above. 
In studying tke preparations, a glass globe filter and con- 
denser, tilled witli a kgkt blue solution of ammoniated copper 
sulpkate, was used, in connection witli a Welsback gas lamp. 
So far as tke writer lias been able to discover, only tliree 
investigators liave so far attempted to cut sections of tkese 
plants —He gl er, Fi scli er, and Wäger. A tliorougk exami- 
nation of tke He gl er preparations, loaned me tlirougk tke 
kindness of Professor G-. Karsten, liave convinced me tkat liis 
sections of Anabaena were entirely too tkick to enable kirn 
to discover from tkem muck tkat was new. His preparations 
sliow, as do also tke pliotograAuires illustrating kis exkaustive 
article, a central body wkicli is so deeplv stained tkat ckromatic 
and ackromatic substances can not be clistinguislied from eacli 
otlier. Judging, liowever, from tke text, He gl er must liave seen 
clearly tlie cliromatin granules lying in tlie acliromatic portion 
of tke central body, as kis description of tkem slioivs. 
Fisclier’s drawings skow tkat kis cross sections of Oscil¬ 
latoria must liave been excellent and some, at least, well stained. 
He gives but two drawings of longitudinal sections of Oscillatoria , 
botk stained witli Delafield's kaematoxykn, figure 42 sliowing 
tlie slime globules, or „red granules“ of Bütsclili, lying im- 
bedded in tke central body, and figure 49, sliowing simply tke 
deeply stained central body alone. 4t may assist us in knding 
a, reason for Fisclier’s decision against tke nuclear nature of 
tlie central body by comparing kis figure 36 witli figure 18 of 
