Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 71. (Budapest 1979)

Domokos, T.: On the morphological changes during ontogenesis of some Hungarian molluscs

1.0 Fig. 5. Diving wall between neighbouring whorl of Planorbidae. — Fig. 6. a = The saline steppe around Szabadkígyós, 8 km from Békéscsaba; b = Ditch in the vicinity of Békéscsaba is 20% greater on the average than that of the specimens of Békéscsaba (Fig. 6). Concerning the traced value, a significant, 25-30%, spread must be reckoned with in both biotas. It can also be seen that the increase of w results in the rounding of the mouth. Anisus septemgyratus ROSSMÄSSLER. I studied the lines of growth of this species earlier (DOMOKOS 1976, 1977, 1978), and found that the whorls rise in the course of their growth step-like. With the growth of the whorls the side line of the mouth inclines more and more to the axis, and the rotundity of the initial whorls gradually decreases and becomes increasingly angular (Fig. 7). The analysis of the radial growth gave a surprising result. The growth can be divided into two phases: a rapid and a slow one (Fig. 8). The exact reason of this is unknown at the present time. Value K

{ of the point of break varies from biota to biota. Factor m

2 is normally in correlation with the final development of the single individual, quasi determining it (?) (Fig. 9). Turbinate form: Chondrula tridens O. F. MÜLLER. Statistics h and hjb of the fully developed specimens are found in Fig. 10. The most frequent value for h is 10 mm, Fig. 7. Shell of Anisus septemgyratus, cross and sagittal section, r

4 = radius of fourth whorl. — Fig. 8. Relationship between K (whorl number) and log 10r; I = primary phase, II = secondary phase. Characteristics: m

x = 0.366 tgcc, m

2 — 0.366 tgß, K

t — whorl number of fracture of curve