American journal of physiology . lace the ectosarc and its striationsappeared, and a typical Stentor resulted. These stages in the for-mation of the peristome, andthe division of the nucleus correspond closelywith a periodical change which Balbiani ^ ob-served in Stentor. He saw the disappearanceof the old mouth and peristome, and their regen-eration, with the attending modification of thenucleus as described above. This experimentrecalls also Loebs^ experiments on the trans-formation of organs among Hydroids, in whichthe material of the polyps was modified intostolons by a contact stimulus, a
American journal of physiology . lace the ectosarc and its striationsappeared, and a typical Stentor resulted. These stages in the for-mation of the peristome, andthe division of the nucleus correspond closelywith a periodical change which Balbiani ^ ob-served in Stentor. He saw the disappearanceof the old mouth and peristome, and their regen-eration, with the attending modification of thenucleus as described above. This experimentrecalls also Loebs^ experiments on the trans-formation of organs among Hydroids, in whichthe material of the polyps was modified intostolons by a contact stimulus, and the processthen reversed. None of these changes was observed in theStentor that were exposed to a higher tempera-ture (25°-28° C), but another process wasnoted. As described by Biitschli^ and others an increase of temper-ature greatly stimulated cell division among the Infusoria. The con- ^ Balbiani: Zoologischer Anzeiger, iv, pp. 312 and ^•Loeb: This journal, 1900, iv, p. 178.^ Bronns Thierreich, i, 3, p. Figure 5. — Firststage in the forma-tion of an activeStentor from tiieresting cell, twelvehours after the tem-perature has becomenormal. Figure 6. — Secondstage in the formationof an active Stentorfrom the resting cell,sixteen hours afterthe temperature hasbecome normal. 126 Arthur W. Greeley. trol specimens, kept at the room temperature, showed very few casesof cell division, but in ^almost every instance, the Stentor began todivide immediately upon being put into the thermostat. The divisionsfollowed in quick succession for from five to seven bi-partitions, with-out a marked diminution in the size of the Stentor. After three orfour hours, division ceased, and the Stentor soon died. This resultindicates an increase of irritability, corresponding with an increaseof water in the cell, and brings out very clearly the antagonism in theeffect upon these organisms of raising and lowering the temperature,the one stimulating cell division and rapid growth, an
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