Table 1.

Normal development of H. trivolvis

Stage name		Stage after Meshcheriakov	Stage,%	Size, mm
				(min - max)
Trochophore	Early	19	20	0.16 – 0.19
	Middle	20	25	0.20 – 0.24
	Late	21	30	0.25 – 0.31
Veliger	Early	22	35	0.32 – 0.40
	Middle	23	45	0.41 – 0.47
	Late “hippo”	24	55	0.48 – 0.56
Metamorphic	Veliconcha	25	65	0.57 – 0.61
		26	75	0.62 – 0.66
		27	85	0.67 – 0.72
Adult-like		28	90	0.73 – 0.78
		29	100	0.74 – 0.79

Interrelations between developmental stages after Mescheriakov [51], timing of embryogenesis in%, and the length of specimens in mm are shown. Five hundred specimens were measured.