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Smith, was first observed by Couch so long since as the year 

 1843, a figure of the same then given by him being reproduced 

 at page Ivii of the introduction to Bell's ' History of the Stalk-Eyed 

 Crustacea/ Ed. 1853. The second and third larval conditions 

 (Figs. 2 and 3) very closely resemble one another, and differ most 

 remarkably from the preceding one in the conspicuous develop- 

 ment of the beak or rostrum, and of the filamentous natatory 

 appendages, or exopodites of the thoracic limbs. Between them- 

 selves these second and third larval conditions are distinguishable 

 by their difference in size, and by the greater numerical develop- 

 ment, in the later phase, of spinous processes upon the dorsal 

 aspect of the abdominal segments. In the fourth phase (Fig. 4) 

 rudimentary abdominal appendages have begun to make their 

 appearance. These become more fully developed in the suc- 

 ceeding phase (Fig. 5) where they share with the thoracic appen- 

 dages, which are now relatively reduced in size, the locomotive 

 function. The corresponding structures developed upon the 

 sixth abdominal segment at the same time convert the hitherto 

 simply spatulate tail into a many-jointed structure, identical in 

 all essential points with that of the adult. With the next ecdysis 

 (Fig. 6) the long antennae make their appearance, the exopodites 

 or swimming appendages of the thoracic limbs have become 

 entirely obliterated, so that the little crustacean is no longer a 

 Schizopod, like the opossum shrimp (Mysis), but is in all respects 

 a typical Macrouran, differing only in its more slender propor- 

 tions from the parent lobster. At this stage of its existence it is, 

 in fact, so lightly constructed that it either walks along the 

 ground or swims in mid-water, after the manner of a prawn, 

 which it much resembles, and it is only with the next shell- 

 casting or ecdysis about a week later, that the limbs and body, 

 becoming relatively heavier, the normal ambulatory mode of 

 existence characteristic of the adult animal is permanently 

 adopted. 



