Key to Vermiform (worm-like) Invertebrates
	Figure 1.  This small worm (10X magnification) looks superficially like a flatworm, but closer inspection (Fig. 1b; approx. 30X magnification) reveals annulations and internal body segmentation. Behavioral movements, including attaching by an anal disc and stretching the body forward, confirm that this is actually a leech (see also Annelida Fig. 2).
	20a		Animal worm-like (vermiform) or grub-like; body segmented or annulated (constricted in rings at regular intervals; may require some magnification; Fig. 1b)	[21]
	20b		Animal vermiform, but lacking multiple constrictions or repetitive external structures that indicate segmentation down the length of the body	[18]
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	21a	(17) & (20)	Vermiform with more than 15 segments, all usually of similar diameter ~ Phylum ANNELIDA	[35]
	21b		Animal more grub-like with fewer than 15 total segments. {Shape somewhat fusiform (like a spindle, tapering down at both ends) or at least fatter through the middle. Larvae ~ Phylum ARTHROPODA ~ Class INSECTA ~ Order DIPTERA	[134]
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	22a	(19)	A single opening to digestive cavity (pharynx) located behind head on ventral surface; gastrovascular cavity with a single anterior branch and two postero-lateral branches. { Small (5 to 30 mm), flat worm with two eyespots on the head located beneath circular non-pigmented areas and between (usually) two triangular lateral projections (auricles). Freshwater streams and ponds. Planarian flatworm ~ Phylum PLATYHELMINTHES ~ Class TURBELLARIA ~ Order TRICLADIDA ~ Family PLANARIIDAE	[23]
	22b		Mouth at front of head and anus near back end. {Small (1 to 30 mm), somewhat flattened worm without auricles, and two to four pairs of eyespots. Freshwater streams and ponds ~ Phylum NEMERTEA ~ Prostoma cf. graecense
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	23a	(22)	Auricles (paired ear-like flaps near head end) are well-defined, arising distinct from lateral margin of body. Dorsal surface covered in gray to brown specks. Eyespots two, well-developed.	[24]
	23b		Auricles weakly developed or more-or-less absent, although body is generally widest across eye-spots	[25]
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	24a	(23)	Auricles elongated, sharply pointed. Worm up to 30 mm long. Streams and pools Dugesia cf. dorotocephala (Woodworth)
	24b		~1 mm by 7 mm long. Freshwater pools and streams flatworm "Type II"
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	25a	(23)	Auricles evident as widening of body across well-developed eye-spots. Color transparent except for white internal organs and dorsal surface flecked with white and light tan, dark brown flecks along midline forming a small loop over mouth area. To 2 x 10 mm flatworm "Type I"
	25b		Auricles absent, body hardly at all wider at eyespots than at mid-point. Eyes weakly developed and close to midline. Color transparent with white organs and numerous small white flecks. 0.5 mm by 4 mm flatworm "Type III"