CHAPTER IV. 



THE METAMORPHOSIS OF ALPHEUS. 



By W. K. Brook and F. H. Hebbick. 



_A 



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



Section I.— The Metamorphosis of Alpheus minor from Beaufort, North Carolina. 



This small species is found in abundiince at Beaufort, Nortli Carolina, and in the Bahama Islands, 

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

 vertical burrows in the sandy mud which forms the bottom of most of the landlocked sounds 

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

 shells. 



Durinji its development, between the time when it hatches from the egj? and the time when it 

 acquires the adult form, it i)asses through a long 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 lind that other species, such as Alpheus iiormani, i>ass through the same metamorphosis, the 

 life history of Alpheun minor may be regarded at the primitive or ancestral life history of the 

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

 by only a few, aud has undergone secondary or recent modilications in the others. 



THK 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 cxopodites of the three pairs of nuixillipeds, 

 and the plumose hairs on the antennules and antenna' are not fully extende<l until after the change. 



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

 the larva during the lirst stage are sliown in PI. xvi, Figs. 4,0, 7, and 8, and IM. xviii, P'ig. 4. In 

 PI. XVI, Fig. 4, is the antenna of the first larval stage. Fig. 6, the first maxilla, Fig. 7, the second 

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

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

 are the plumose exopotlites of the antenna' and of the three pairs of maxillipeds. There are uo 

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

 entirely uncovere<l. 



The larva has all its appendages fully develoi)ed and functional as far ba<;k as the third pair of 

 maxillipeds. Following these are three bud like rudinuuits of the first, second, and fifth i)airs of 

 thoracic limbs, aud j)osterior 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 



Ml 



