The accompanying representation of the embryo of _Squilla_ shows that it possesses a long, segmented abdomen without appendages, a bilobate tail, six pairs of limbs, and a short heart; the latter only pulsates weakly and slowly. If it acquires more limbs before exclusion, the youngest larva must stand on the same level as the youngest larva of _Euphausia_ observed by Claus. Fig. 34. Embryo of a Squilla, magnified. a. heart. Fig. 35. Older larva (Zoëa) of a Stomapod, magnified. Fig. 34. Embryo of a Squilla, magnified. _a._ heart. Fig. 35. Older larva (Zoëa) of a Stomapod, magnified. Of the two larval forms at present known which are with certainty to be ascribed, if not to _Squilla,_ at least to a Stomapod, I pass over the younger one[7] as its limbs cannot be positively interpreted, and will only mention that in it the last three abdominal segments are still destitute of appendages. The older larva (Fig. 35), which resembles the mature Squilla especially in the structure of the great raptorial feet and of the preceding pair, still wants the six pairs of feet following the raptorial feet. The corresponding body-segments are already well developed, an unpaired eye is still present, the anterior antennæ are already biramose, whilst the flagellum is wanting in the posterior, and the mandibles are destitute of palpi; the four anterior abdominal segments bear biramose natatory feet, without branchiæ; the fifth abdominal segment has no appendages, and this is also the case with the tail, which still appears as a simple lamina, fringed on the hinder margin with numerous short teeth. It is evident that the larva stands essentially in the grade of Zoëa. [1] Authorities are cited only for facts which I have had no opportunity of confirming. [2] Bell (‘Brit. Stalk-eyed Crust.’ p. xlv) considers himself justified in “eliminating” Thompson’s observation at once, because he could only have examined ovigerous females preserved in alcohol. But any one who had paid so much attention as Thompson to the development of these animals, must have been well able to decide with certainty upon eggs, if not too far from maturity or badly preserved, whether a Zoëa would be produced from them. Moreover, the mode of life of the Land-Crabs is in favour of Thompson. “Once in the year,” says Troschel’s ‘Handbuch der Zoologie,’ “they migrate in great crowds to the sea in order to deposit their eggs, and afterwards return much exhausted towards their dwelling places, which are reached only by a few.” For what purpose would be these destructive migrations in species whose young quit the egg and the mother as terrestrial animals? [3] In a memoir on the metamorphoses of the Porcellanæ I have erroneously described this appendage as the “flagellum.” [4] _Glaucothoë Peronii,_ M.-Edw., may be a young and still symmetrical _Pagurus_ of this kind.