THE GENUS LERN^ODISCUS. 433 



Colleteric glands (oviducts) paired and convoluted. 



Genital openings asymmetrically distributed owing to rotation of mesentery 

 (see figs. 3, 4, 5, 6, 7, 8.) 



Nauplius with somewhat elongated and curved frontal horns. 

 Parasitic on Symmetrical Decapoda Anomura. 



L. PORCELLAN^, F. MuUer (1). Host: Porcellana sp. from Brazil. 

 Visceral mass purplish, lappets of mantle very conspienous and indented. 



L. GALATHEiE {G. W. Smith {2)). Hosts: Galatliea dispersa at Naples 

 (Smith (2)), Griilf of Gascony (Guerin-Ganivet (5)). 



Galatliea intermedia, Norway (Smith (2)), Saint Vaast-la-Hougue and 

 Gnlf of Gascony (Guerin-Ganivet (5)), Banyals (Kollmann (3 & 4)). 



Visceral mass yellow ; lappets of mantle few and irregular. 



L. STRIGOS^. Host: Galatliea strigosa at Naples (Smith (2)). 

 Distinguished from above only by larger size, and may probably be 

 included under L. galathece. 



L. MUNiP^ [ — Triangidas munidoi (G. W. Smith (2)). Hosts: Munida 

 hamflca from Norway (Smith (2)), and from the Shetlands (Professor W. 

 A. Herdman). Gulf of Gascony and Brittany coasts, and African coast, 

 south of Cape Bojador (Guerin-Ganivet (5)). 



Visceral mass yellow. Lappets of mantle few and deeply indented. 

 Mantle-opening deflected very definitely to right side. Colleteric glands 

 (= oviducts) advanced well on to visceral mass in neighbourhood of mantle- 

 opening. Relations of mantle and of openings of testes and of nerve-ganglion 

 the same as in L. galathece. 



Note. — It is clear from the meagre distinctions which it is possible to make 

 between these various parasites attached to different Galatheids that it is 

 very doubtful how far they represent good species. It is, indeed, doubtful 

 what criterion of a good species there can be in animals which reproduce by 

 a continuous round of self-fertilization, and are only distinguished from one 

 another by slight differences of shape and sometimes of colour, and which 

 offer no morphological features of outstanding importance in which they 

 jdifFer. I have already dealt with this fundamental difficulty in my monograph 

 (2) pp. 166 & 167. 



LINN. JOURN, — ZOOLOGY, VOL. XXXII, 35 



