44 



Guide to Crustacea. 



Table-case 

 No. 6. 



Fig. 25. 



ArctuYua bdJjUiii, female, carrying a cluster of young one« on its antennae. 

 [Table-case No. G.] 



terrestrial species and their marine relatives. PorccUio scaber 

 (Fig. 26) is one of the very coromon garden species. 



The Isopods helonging to the Suh-order Epicaridea are all 

 parasitic on other Crustacea, and their structure presents, in the 

 adult state, a great variety of modifica- 

 tions. The two sexes are often very dis- 

 similar in size and shape, and some 

 species are hermaphrodite. A specimen 

 of the common Prawn {Leander serratus) 

 is exhibited which has, on one side of 

 the carapace, a swelling due to the pre- 

 sence in the gill-chamber of the parasite 

 BopyruH squiUannn. The female of the 

 parasite, taken out of the gill-chamber, is 

 shown alongside. The male, in this 

 species, is almost microscopic in size, and 

 is commonly found clinging to the under 

 side of tlie female. 



A still more remarkiil)lo form is slmwn 

 in tlie drawings of I'tirtiiiiioii maciifidis, 

 a pai'asite of the common Shore-crab, 

 ('iirci)iiis iiinviKis. The figui'(! on the right 



Fui. yC). 



J'oncU'u) sciilirr, female, 

 doi'sal view, enlarged. 

 (From Lankester's 

 " Treatise on Zoology," 

 after Sars.) 



