226 PROCEEDINGS OF THE NATION AL .MUSEUM. vol.30. 



Plate 32. 

 The free-swimming larva, first copepodid stage. 



Fig. 22. Veutral view of first copepodid larva, showing appendages. 



23. Dorsal view of same. 



Plate 33. 



The second copepodid stage. 



Fig. 24. Side view of male larva. 



25. Dorsal view of same. 



26. Side view of antennae and mouth parts. 



27. Side view of female larva. 



28. Dorsal view of same. 



29. A first antenna with only two joints and two terminal setae. 



30. Second antenna. 



31. Mouth-tube, mandible, and first maxilla. 



Plate 34. 

 Longitudinal sections of male and female second copepodid larvse. 

 The lettering of the digestive, excretory, and nervous systems applies equally to 

 both figures; that of the reproductive organs is of necessity peculiar. 



Fig. 32. The male: a\, nerve to first antenna; dm., dorso-ventral muscles; fg., 

 frontal gland; gc, gland cells; i, intestine; iog, infra-oesophageal gang- 

 lion; h, cellular mass or plug, Claus' "Kornchenhaufen;" lb., nerve to 

 labium; Im., longitudinal muscles; md, nerve to mandible; m;>gr.,maxil- 

 lipedal gland, median center, the lateral center being at Ic; mx' ., nerve 

 to second maxilla; mxp., nerve to maxilliped; n, nerve to frontal and 

 maxillipedal excretory glands; oe, oesophagus; p., plug of secretion of 

 frontal gland filling hole left by removal of attachment filament; p c, 

 proctodeum; t., testes; vc, ventral cord of nervous system. 

 33. The female: a, anus; a^^, nerve to second antenna; Im, longitudinal mus- 

 cles; m,pg^, nerve to maxillipedal gland; mx, nerve to first maxilla; 

 o., ovary; s, stomach; sm., sphincter muscle; sog., supra oesophageal 

 ganglion; up., uterine processes of the oviduct. 



Plate 35. 



Sections showing internal anatomy. 



Fig. 34. Diagonal section through head of metanauplius larva, showing frontal 

 gland and attachment filament; a., first antenna; c, coils of filament; e., 

 rudimentary eye;fg., frontal gland; m., muscles of swimming legs; ms., 

 mushroom enlargement at anterior end of filament; p., peg at proxi- 

 mal end of filament; w., wall of egg sac. 



35. Beginnings of male reproductive organs; din., dorsoventral muscles; fd., 



free portion of the deferent duct; t., testes; vd., deferent duct. 



36. Beginnings of female reproductive organs; eg., cement gland; dm., dorso- 



ventral muscles; o., ovary; od., oviduct; up., uterine processes. 



37. The maxillipedal gland of an adult male; d., corkscrew duct; Ic, lateral 



center of gland; mc, median center; mpg., main portion of the gland; 

 mxg., maxillary gland; sm., supporting muscles. 



Plate 36. 



Young adults of Achtheres amhloplitis. 



Fig. 38. Side view of sexually mature male, attached to spine of gill arch 



39. Mouth parts of same. 



40. First maxilla. 



41. Mandible. 



42. Side view of young female. 



43. Antennae and mouth parts of same. 



44. Section through the tips of the second maxillae; af., attachment filament; 



Im., longitudinal muscles; mx., wall of maxilla. 



