Facts and Arguments for Darwin

9781428088955

1428088954

To the question, how far the development of Ligia is repeated in the other Isopoda, I can only give an unsatisfactory answer. The curvature of the embryo upwards instead of downwards was met with by me as well as by Rathke in Idothea, and likewise in Cassidina, Philoscia, Tanais, and the Bopyridae, --indeed, I failed to find it in none of the Isopoda examined for this purpose. In Cassidina also the first larval skin without appendages is easily detected; it is destitute of the long tail, but is strongly bent in the egg, as in Ligia, and consequently cannot be mistaken for an "inner egg-membrane."