FIGURE 13. Cetochilus septentrional. (After Grobben, from Faxon.) 

 Copepoda, Natantia. Nauplius; just hatched; ventral view. 



FIGURE 14. Adheres percarum. (After Claus, from Faxon.) Co- 

 pepoda, Parasitica. Larva at the time it leaves the egg, with only two 

 anterior unbranched pairs of appendages of the typical nauplius present. 

 Under the skin are the rudiments of six pairs of appendages ; ///, man- 

 dibles; IV, maxillae; V, VI ', maxillae; VII, VIII, swimming feet. 



FIGURE 15. Balanus balanoides. (After Hoek, from Faxon.) Cirri- 

 pedia. Nauplius. 



FIGURE 16. Lerncediscusporcellance. (After F. Miiller, from Faxon.) 

 Cirripedia, Rhizocephala. Nauplius; ventral side; showing outline of 

 dorsal shield. 



FIGURE 17. Sacculina purpurea. (After F. Miiller, from Huxley and 

 Balfour.) Cirripedia, Rhizocephala. 



FIGURE 18. Cyprus ovum. (After Claus, from Faxon.) Ostraeoda. 

 First larval (nauplius) stage, with bivalve shell and unbranched second 

 and third pairs of appendages. 



FIGURE 19. Nebalia Geoff royi. (After Metschnikoff, from Faxon.) 

 Leptostraca. Side view of the so-called nauplius stage of the embryo 

 within the egg. Rudiments are present of the two pairs of antennas (/. 

 //) and the mandibles (///). 



FIGURE 20. Euphausia. (After Metschnikoff, from Faxon.) Schi- 

 zopoda. Nauplius ; just hatched. 



FIGURE 21. Euphausia. (After Metschnikoff, from Faxon.) Schi- 

 zopoda. Nauplius at a later stage; ventral view ; mt, metastoma; IV, V, 

 maxillae ; VI, maxilliped. In the next, or Protozoen, stage the append- 

 ages (IV, V, VI) are true phyllopodiform feet. 



FIGURE 22 Mysis ferruginea. (After Van Beneden, from Faxon.) 



Schizopoda. Nauplius-like embryo ; side view. The appendages are 

 unsegmented, and the third pair is quite rudimentary. A number of later 

 metamorphoses are undergone in the nauplius skin, until the full number 

 of appendages is developed. 



FIGURE 23. Peneus. (After F. Miiller, from Faxon.) Decapoda, 

 Macroura. Nauplius; from dorsal side. 



FIGURE 24. Lucifer. (After Brooks, from Faxon.) Decapoda, Ma- 

 croura. Ventral view of embryo artificially removed from the egg ; / V, 

 V, VI, buds representing the two pairs of maxillae and first pair of max- 

 illipeds of the adult. 



FIGURE 25. Palcemon. (After Bobretzky, from Faxon.) Decapoda, 

 Macroura. Nauplius stage of embryo within the egg. 



FIGURE 26. Astacus fluviatilis. (After Reichenbach, from Faxon.) 

 Decapoda, Macroura. Nauplius stage of embryo. 



FIGURE 27. Limulus polyphemus. (After Kingsley.) Xiphosura. 

 Ventral view of embryo ; showing the budding of the legs. 



FIGURE 28. Limulus polyphemus. (After Packard, from Balfour.) 

 Xiphosura. Ventral view of embryo in the egg ; showing the rudiments 

 of six pairs of legs ; m, mouth. 



FIGURE 29. Limulus polyphemus. (After Packard, from Balfour.) 

 Xiphosura. Oblique side view of embryo, with the mouth and rudimen- 

 tary limbs on the ventral plate. 



The figures of embryonic Limulus are introduced for comparison. 

 They are so different from the nauplius that detailed notice seems un- 

 necessary. 



