Morphogenesis and Homology in Arthropod Limbs

Arthropods exhibit highly diverse limb morphologies rangingfrom unbranched walking legs to multibranched swimming paddles.Understanding morphogenesis in structurally diverse limbs canbe useful for ascertaining homologies between limbs. Structurallysimilar limbs have been produced by different evolutionary modificationsof morphogenesis in certain cases. Whereas it is easy to supportthe claim that whole arthropod limbs are homologous structures,I demonstrate that it is not always possible to draw well-foundedhomologies between parts of different limbs. This result isimportant with regard to general models of appendage developmentand evolution in arthropods because it clarifies contradictoryexplanations based exclusively on gene expression data.     

THE EFFECT OF MOLLUSCICIDES ON THE CONSUMPTION OF BAIT BY SLUGS

The consumption of bait by Agriolimax reticulatus and Milaxbudapestensis has been measured. Although the addition of methiocarbto the bait may reduce the numbers of Milax which eat it, themain effect of adding poison is to reduce markedly the amountof bait consumed. This effect is discussed in relation to thepoison concentration in the bait, the consequent ingestion ofpoison, and the cause of the reduction. (Received 11 September 1979;