548 



BULLETIN .U, 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 



o 



d 



Fig. 592. — Argeia pugettensis. First incubatory plate from specimens found on: a, Necto- 



CRANGON CRESSA FROM OFF CaPE NewENHAM, ALASKA. X 9^^. 6, NeCTOCRANGON CRASSA FROM 



Alaska, x 9^. c, Crago nigromacul-^ta from San Diego Bay, California, x 9j. rf, Crago 

 nigrkatda from off Cape Johnson, x 9j. 



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

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

 not be present. When present they are usualU^ smaller than the first 

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



discern. The marsupial plates are 

 larger than in the preceding stage, 

 ])ut not fully developed. The in- 

 cul)ator3' pouch never carries eggs 

 in either of these stages. The male 

 is similar to the male of the adult 

 female. 



Specimens of l)oth immature 

 stages were found on the same 

 species and genera of host as the 

 adult females. 



A male in the crvptoniscan stage 

 was found on one iuuuahire female 

 (in first post-larval stage). 



Thoracic processes of adult fe- 

 VI ale. — In the adult female the 

 thoracic processes ma}- 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 

 i n the very young female or as in the 

 figure given hy 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 difi'erent 

 species and genera of host, but it is also tru«^, of those found on the 

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



Fig. 593.— Argeia pugettensis. First incu- 

 batory lamella from specimen found on: 

 n, Crago communis from Straits of Fuca. 

 X 14. 6, Crago communis from Akutan 

 Island, Alaska, x 14. c, Nectocrangon 

 alascensis from southwest of Sannakh 

 Islands, Alaska, x 14. d, Crago dalli from 

 south ok Amak Island, x H. 



