Change in inheritance in echinoid hybrids

Abstract

In 1932 crosses were made at Plymouth between Psammechinus miliaris ♀, both Z-type (from the shore) and S-type (from Eddystone), and Echinus esculentus ♂. The larvae from the S eggs differed in size and shape from those from the Z eggs (cf. Figs. 1,2 with 3–6). None of the hybrid plutei possessed the green pigment of P. miliaris, nor the posterior epaulettes of E. esculentus. Some of the larvae (Figs. 3, 4) had a posterior pedicellaria, like E. esculentus, in others this organ was missing (Figs. 1, 2, 5, 6). Some of these plutei were preserved, others went through metamorphosis. Healthy larvae of these combinations (00+ and 000) have not hitherto been described. The results are compared with those of previous authors (see table, p. 100). Some possible causes of change of inheritance in different years are discussed.