Mycetomorpha. 591 



Diagnosis of Genus Mycetomorpha. 



Parasitic on ventral surface of abdomen of a shrimp Crangon 

 communis. Sollt ary. 



Exte mal body flattened and musliroom sliaped, length 

 greater than breadth, colour pale yellow, borders fringed with 

 numerous sliort lobes. 



Rootsysteni not widely distributed, situated under nerve 

 cord of host, colourless. 



Mantle smooth, very thin, with feeble rausculature. 



Mantle cavity enormously enlarged and produced into the 

 lateral lobes which together with the main cavity are filled with 

 Cypris larvae. 



Mantle opening small, situated at apex of a tubulär structure 

 with narrow lumen, the mantle duct on left side of visceral mass. 



Visceral mass very small in relation to the total size of 

 body, displaced to the apparent left side of the animal, forming a 

 semicircular curve. 



Peduncle short, runs obliquely into body of host pointing 

 anteriorly: chitin of the ring continued anteriorly as a median spike. 



Lacuna of rootsystem communicates with visceral mass far 

 posteriorly by dorsolateral mesentery. Main mesenteric connection 

 runs along left side. 



Ganglion not known. 



Testes absent. 



Colleteric glands possibly represented by paired discs on surface 

 of visceral mass. 



Female ducts absent. 



Larval males absent. 



M. vancouverensis. Ohara cters of species those of genus. 



A note on the Sexual Condition in Sylon. 



Sylon has already been recorded from Puget Sound by W. T. Cal- 

 MAN (2j who described S. hippolytes as occurring on Tlippolyte hrevi- 

 rostris, Pandaliis danae and Sderocramjon munitus. A large number 

 of individuals were collected in 1909 by Miss Kathleen Haddon 

 and in 1911 by myself while working at the Marine Biological 

 Station of the University of ^^'ashington, situated at Friday Harbour 

 in the San Juan Archipelago. In his monograph on the Rhizocephala 

 Mr. Smith describes Sylon as structurally a female and not a herm- 



