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looser one, that differs each time in many structural points 

 from its predecessor. As determined by my own experi- 

 ences, such a changing of the skin, or "ecdysis," as it is 

 technically termed, is effected no less than half a dozen 

 times before the little animal arrives at the ambulatory con- 

 dition, and takes upon it the form and features of the 

 parent. This chapter in the life-history of the young 

 lobster is of the most interest, perhaps, when studied by 

 aid of the recently kindled, but ever-increasing, light of the 

 doctrine of evolution. In its onward progress towards the 

 form and proportions of a typical lobster it is thereby found 

 to pass through conditions that in former times were re- 

 garded as distinct animals belonging to less highly organ- 

 ised groups of the Crustacea than the parent animal. 



Thus, when liberated from the egg, the little crustacean, 

 designated a " Zoea," has no abdominal appendages, and 

 swims through the water by means of the external branch- 

 lets, or " exopodites " of its thoracic limbs, and in this 

 respect resembles the so-called Opossum Shrimp (Mysis) 

 referable to the order Schizopoda. This condition is main- 

 tained through several successive skin-castings, or ecdyses, 

 the abdominal appendages, or swimmarets, however, grad- 

 ually developing, and the thoracic swimming organs be- 

 coming simultaneously reduced. At or about the sixth 

 cast these last-named structures have entirely disappeared ; 

 the little animal swims through the water with the aid only 

 of its abdominal swimmarets, and is to all intents and pur- 

 poses a small prawn (Pal&mon). The internal elements, or 

 " endopodites " of the primarily bifid thoracic limbs have, 

 meanwhile, developed into true legs, so that, after the 

 manner of a prawn, the young lobster can either walk, upon 

 the ground or swim in midwater. It is with the next 

 ecdysis only that the animal becomes a typical lobster, re- 



