. Fresh-water biology. Freshwater biology. THE FREE-LIVING FLATWORMS (TURBELLARIA) 357 92 (93) Angle of head 50° to 60°. Color a very dark sepia-brown almost black by reflected light. . Planaria agilis Stringer 1909. Length of immature worms usually not over 18 mm. Mature specimens collected have meas- ured 30 mm. Well fed specimens in aquaria have attained a length of 55 mm. Color usually very uniform. ^ Ventral surface but little lighter than dorsal. One variety found only in one locality and with uniformly colored specimens, shows sharply defined non-pigmented spots. Under lens a clear ligh
. Fresh-water biology. Freshwater biology. THE FREE-LIVING FLATWORMS (TURBELLARIA) 357 92 (93) Angle of head 50° to 60°. Color a very dark sepia-brown almost black by reflected light. . Planaria agilis Stringer 1909. Length of immature worms usually not over 18 mm. Mature specimens collected have meas- ured 30 mm. Well fed specimens in aquaria have attained a length of 55 mm. Color usually very uniform. ^ Ventral surface but little lighter than dorsal. One variety found only in one locality and with uniformly colored specimens, shows sharply defined non-pigmented spots. Under lens a clear light-brown ground with fine dark brown, almost bkck pigment granules, either quite uniformly distributed or arranged so as to give the appearance of a very close net work. Circum-ocular spaces either oval or sUghtly pointed at outer anterior region and placed just in front of or in line with the anterior margins of cephalic appendages. Some with light areas on posterior margins of cephalic appendages, others with auricles uniformly pigmented. A light median streak sometimes present. Lateral margin of head with a distinct inward curve. just back of tip, also at junction of head with cephalic appendages. Wider just in front of appendages than at any point posterior to them except in large specimens which are of about same width through pharyngeal region. Mature specimens much broader proportionally than immature. Asexual reproduction the usual method of propagation in most localities. Very restless and active. Collected from small ponds and spring-fed brooks either among algae or on sandy bottom and often where water flows swiftly. Neb., Mo., S. Dak., Wis., and Cal. Fig. 632. Planaria agilis. (A) Immature specimen from life. X8. {B) Sexual organs, dorsal view: m, uterus: m^ uterus tube; 0, oviduct; gp, genital pore; a, atrium; sv, seminal vesicle; vd, vas deferens: pi, cirrus lumen; la, limit of atrium. Much en- larged. (After Stringer.) 93 (92) Angle of head about 45°. Color red
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
