BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



developed at this stage. The marsupial plates are small and just 



developing. The male is similar to the male found on adult female. 



Immature female of a more advanced stage has the thoracic processes 



well developed, although perhaps not quite as long as in the preceding 



a be d 



FIG. 592. ARGEIA PUGETTENSIS. FIRST INCUBATORY PLATE FROM SPECIMENS FOUND ON: a, NECTO- 



CRANGON CRES8A FROM OFF CAPE NEWENHAM, ALASKA. X 9J. 6, NECTOCRANGON CRASSA FROM 



ALASKA, x 9J. c, CRAGO NIGROMACULATA FROM SAN DIEGO BAY, CALIFORNIA, x 9}. d, CRAGO 



NIGRICAUDA FROM OFF CAPE JOHNSON. X 9r- 



stage. The outer pleopoda and uropoda are small, but all developed. 

 The first two inner pleopoda are present; the other three may or may 

 not be present. When present they are usually smaller than the first 

 two, decreasing in size to the fifth pair, and sometimes difficult to 



discern. The marsupial plates are 

 larger than in the preceding stage, 

 but not fully developed. The in- 

 cubatory pouch never carries eggs 

 in either of these stages. The male 

 is similar to the male of the adult 

 female. 



Specimens of- both immature 

 stages were found on the same 

 species and genera of host as the 

 adult females. 



A male in the cryptoniscan stage 

 was found on one immature female 

 (in first post-larval stage). 



Thoracic processes of adult fe- 

 male. In the adult female the 

 thoracic processes may be quite re- 

 duced. In some specimens these 

 processes are well developed, 

 though never in all the specimens 

 examined were they found as long as 

 in the very young female or as in the 



figure given by Dana of the adult female. In other specimens these 

 processes are very small, and yet in many they were not even present. 

 Not only is this variation found in specimens taken from different 

 species and genera of host, but it is also true of those found on the 

 same species and genus of host. As a result of this observation on a 



FIG. 593. ARGEIA PUGETTENSIS. FIRST INCU- 

 BATORY LAMELLA FROM SPECIMEN FOUND ON: 



a, CRAGO COMMTJNIS FROM STRAITS OF FUCA. 

 x 14. b, CRAGO COMMUNIS FROM AKUTAN 

 ISLAND, ALASKA, x 14. c, NECTOCRANGON 



ALASCENSIS FROM SOUTHWEST OF SANNAKH 



ISLANDS, ALASKA, x 14. d, CRAGO DALLI FROM 

 SOUTH OF AMAK ISLAND, x 14. 



