10 



NATURAL HISTORY OF ARTHROPODS. 



several distinct types of development, which, omitting several exceptions, may be 

 here briefly described. The barnacles, Entomostraca, and a few examples of other 



gi-oups, hatch when but three pairs 

 of legs are developed. This stage 

 of the young is known as the I7au- 

 plius (Fig. 12), this term having 

 been applied to one of these larval 

 forms by Otto Fabricius Milller, a 

 Danish naturalist, under the im- 

 pression that it was an adult. 

 From this the use has extended, 

 until now a larval crustacean with 

 three pairs of limbs, the two pos- 

 terior two-branched, a single median 

 eye, a large upper lip, and gener- 

 ally an unsegmented body is im- 

 plied by this term. In another type 

 the young crustacean hatches in 

 the form known as a Zoea (Fig. 

 13), named by Bosc, with the same 

 imj)ression as that to which we owe 

 the term nauplius. The zoea is 

 characterized by the presence of a 

 large carapax, sometimes arnied 

 with long spines. The abdominal 

 segments are well developed, but 



Pig. 12. — Nauplius of Canthocamptus. A, Antennulse. a. Anus. 

 Aiu Antennae. e?i. Endopodite. ex. Exopodite. L, Labrum, 

 M. Mandible, o. Ocellus, s. Stomach. 



Figs, is and 14. —Front and side view of zoea of Neptanm. a. Abdomen. A. Antennulse. An. Antennae, e. 

 Carapax. d. Dorsal spine. E. Eye. L, Labrum. 2. Lateral spine. w,p^. First maxilliped. mjfi. Second 

 maxilliped, r. Bostrum. t. Telson. 



