III. Additional observations on the development of apteryx

Since communicating my previous observations on this subject to the Royal Society (1), I have received from the collector (R. Henry) to whom I owe most of my material, three embryos of Apteryx austrlis, which fill important gaps in the series of developmental stages formerly studied, and serve to correct one or two erroneous conclusions to which I was led by having, in so many cases, only a single specimen of each stage. The youngest of the three embryos is as nearly as possible intermediate in age between Stages E and F of my former paper: I shall speak of it as Stage E'. The second is slightly more advanced than Stage F, and will be called F'.