CHAPTER IV. 



THE METAMORPHOSIS OF ALPHEUS. 



By W. K. BROOK AND F. H. HERRICK. 



(With Pis. I, II, IV, XVI to XXIV. ) 



SECTION I. THE METAMORPHOSIS or ALPHEUS MINOR FROM BEAUFORT, NORTH CAROLINA. 



This small species is found in abundance at Beaufort, North Carolina, and in the Bahama Islands, 

 and it is no doubt widely distributed along our southern coast. At Beaufort it is found in shallow 

 vertical burrows in the sandy mud which forms the bottom of most of the land-locked sounds 

 between tide marks. It is also met occasionally in shells, and under loose stones and oyster 

 shells. 



During its development, between the time when it-natches from the egg and the time when it 

 acquires the adult form, it passes through a lung metamorphosis, divided into many stages. Its 

 life history has been traced by one of the authors at Beaufort, and by the other at Nassau, and the 

 individuals from both these localities pass through exactly the same series of changes. As we 

 also find that other species, such as Alpham normani, pass through the same metamorphosis, the 

 life history of Alplieux minor may bo regarded at the primitive or ancestral life history of the 

 genus, which originally characterized all the species ; although it is now retained in its perfect form 

 by only a few, and has undergone secondary or recent modifications in the others. 



THE FIRST AND SECOND LARVAL STAGES. 



The stage in which the larva hatches from the egg is of very short duration, as it molts and 

 passes into the second stage within a few hours after hatching. No drawings of it were made 

 before the change, but this is very slight, and the description of the second stage holds true in all 

 essentials of the first stage, except that the tips of the exopodites of the three pairs of maxillipeds, 

 and the plumose hairs on the autennules and antenna 5 , are not fully extended until after the change. 



The second larval stage is shown in PI. xvi, Fig. 2, and in PI. xvn, Fig. 2, and various organs of 

 the larva during the first stage are shown in PI. xvi, Figs. 4, 6, 7, and 8, and PI. xvin, Fig. 4. In 

 PI. xvi, Fig. 4, is the antenna of the first larval stage, Fig. G, the first maxilla, Fig. 7, the second 

 maxilla, Fig. 8, the mandible, and Fig. 4 of PI. xviii, the first maxilliped. As shown in PI. xvil, 

 Fig. 2, and in PI. xvi, Fig. 2, the locomotor organs of the larva during the first and second stage 

 are the plumose exopodites of the anteiuiie and of the three pairs of maxillipeds. There are no 

 functional appendages posterior to the maxillipeds, and the large eyes are freely movable and 

 entirely uncovered. 



The larva has all its appendages fully developed and functional as far back as the third pair of 

 maxillipeds. Following these are three bud-like rudiments of the first, second, and fifth pairs of 

 thoracic limbs, and posterior to these a long tapering abdomen, divided into six segments, there 

 being at this time no joint between the telsou and the sixth abdominal segment. During the first 



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