Journal of morphology . se structures arc most strictly lateral inposition (Spirostomum, Blepharisma) will occupy the lowestplace, and the others (Condylostoma, CHmacostomum, Stentor)be arranged according as the zone becomes more and moreterminal, and as the peristome (or its physiological equivalent,the frontal field) increases in breadth and becomes more andmore circumscribed by the zone. This much being attainable by comparative anatomy, doesthe ontogeny of one of the higher forms { Stentor) yield anyevidence for or against the arrangement given in Fig. comparing the various sta
Journal of morphology . se structures arc most strictly lateral inposition (Spirostomum, Blepharisma) will occupy the lowestplace, and the others (Condylostoma, CHmacostomum, Stentor)be arranged according as the zone becomes more and moreterminal, and as the peristome (or its physiological equivalent,the frontal field) increases in breadth and becomes more andmore circumscribed by the zone. This much being attainable by comparative anatomy, doesthe ontogeny of one of the higher forms { Stentor) yield anyevidence for or against the arrangement given in Fig. comparing the various stages in the evolution of the zoneand frontal field of the proximal zooid of 5. c(2rideiis (PI. XXIV,Figs. 26-36) with the series of lower forms (Fig. Ill, a-d), wesee that the successive positions taken by the new organula inquestion correspond quite accurately with the phylogeneticdevelopment of these structures. An exception is seen in thecase of the peristome. This appears as a narrow band along 520 JOHNSON. [Vol. VOL. No. 3-] MORPHOLOGY OF THE STENTORS. 521 the right side of the zone, and a narrow band it remainsthroughout. It is a case of a rudimentary organ persistingafter its function has been assumed by another structure. The evolution of the zone and frontal field does not end withStentor, although in this genus these structures are completelyterminal. In Folliculina the field is produced into two lateral,ear-like appendages. (Fig. Ill, /.) Unfortunately, we lacksufificient information regarding the evolution of the new zonein Folliculina to determine whether it has a Stentor-like stageor not ; but the brief account of the fission by Mobius (86)shows that it is very aberrant, and obviously adjusted to thepeculiar mode of life and highly-modified frontal field of thisform. It is therefore improbable that it will reveal much inregard to the phylogeny of Folliculina. C. Regeneration. One of the most remarkable events in the life-history ofStentor is the periodic renewal of
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