In the year of Dr. Andrews' first visit to the island (1898) this migration occurred in January. On a subsequent visit to the island in 1908 he obtained specimens of a large Megalopa larva (see p. 70) which occurred in enormous quantities in the sea shortly after the migration, and also of a small Crab which appeared in similar numbers at a slightly later date. It seems practically certain that these larvæ and young are those of _Gecarcoidea lalandii_. A second species of Land Crab, _Cardisoma hirtipes_, found on Christmas Island, has very different habits from the foregoing. Dr. Andrews says of it: "In this island, at any rate, this species must be regarded as a fresh-water form, and, in fact, when a specimen was seen it might be taken as an indication that fresh water was not far off. It lives in deep holes in the mud at the sides and bottom of the brooks." Dr. Andrews tells me that he never saw this species at or near the sea (in marked contrast to _Gecarcoidea_), and this agrees with the observations of other travellers on species of the genus _Cardisoma_, so that the breeding habits remain unknown. There is every probability, however, that in this case, also, the young stages are passed in the sea. The student will find, in many textbooks on zoology, the statement that some Land Crabs of the genus _Gecarcinus_ develop without metamorphosis. Although it is impossible, with our present knowledge, to state definitely that this is not the case, there is absolutely no evidence to support it, and it is an interesting example of the way in which erroneous statements sometimes gain currency in science.[3] It is based upon the fact that in 1835 Professor J. O. Westwood described the early stages of "a West Indian Land Crab," in a paper "On the Supposed Existence of Metamorphosis in the Crustacea," published in the Transactions of the Royal Society. Professor Westwood found that the embryos extracted from the egg possessed all the appendages of the adult except the swimmerets, and that young specimens clinging to the abdomen of the parent were perfectly-formed little Crabs. The specimens which he described were sent to him by the Rev. Lansdown Guilding, of St. Vincent, who also deals with the subject in a note published in the _Magazine of Natural History_ in the same year. Neither Westwood nor Guilding refers to the Crab as a _Gecarcinus_, although Guilding calls it the "Mountain Crab," a name which Patrick Browne in 1756 gives to the _Gecarcinus ruricola_ of Jamaica. So far as I am aware, the first writer to refer to Westwood's Crab as a _Gecarcinus_, was Professor T. Bell, who in his "British Stalk-eyed Crustacea," published in 1853, states that some of the original specimens had come into his possession. They consisted of the detached abdomens of female Crabs, with eggs and young adhering to them. It would be by no means easy to identify the species of Crab to which a detached abdomen belonged, and there is nothing in