11 X Systematic guide to the genera and species of Rhizocephala, with anatomical diagnoses. 



Ring of attachment pierces mesentery near the anterior end, is very wide and disc-like. 



(Plate 8 tig. 5.) 

 Colleteric gland median, unpaired, highly branched. (Plate S fig. 6.) 

 Testis median, unpaired, showing no signs of degeneration. (Plate 8 figs. 7 — 8.) 

 Nauplius unknown. 

 Endoparasitic development unknown. 

 Larval males unknown. 

 Parasitic on Decapoda Anomala iPaguridae). 



C. paguri (Lii.ljeborg [4]). Hosts, Ewpagurus bernhardus from Bohuslan by Lilljeborx;, 

 E. bernhardus from Kattegat and E. pubescens from Boreal Seas seen by myself at Kjobenhavn. 



Remarks. Through the kindness of Dr. H. J. Hansen I was enabled to examine several 

 specimens of this hitherto almost unknown genus, and to satisfy myself as to the chief points 

 in its anatomy. The parasite has the appearance of a Peltogaster, being fixed in a similar 

 position on the Hermit-Crab's abdomen; it is usually solitary, but two or three specimens may 

 be present on one host. Its internal anatomy however differs greatly from that of Peltogaster, 

 as shown by the diagnosis given for the genus. 



The most interesting feature in its structure is the presence of a single testis, enor- 

 mously developed and showing no signs of the degenerative hypertrophy of its cells as in all 

 other Rhizocephala. I have already called attention to this feature in Chapter 2 and referred 

 the reader to the transverse sections on Plate 8 figs. 7 and 8. 



The colleteric gland (Plate 8 figs. 5 and 6) is situated at the anterior end of the vis- 

 ceral mass. 



Owing perhaps to the imperfection of my series of sections towards the extreme anterior 

 edge of the visceral mass I could not observe the nervous system. 



I also did not observe an opening of the testes into the mantle cavity, and it appears 

 to me more than probable that the eggs are fertilized in the ovary before passing through 

 the colleteric gland. 



The absence of a mantle opening makes it probable that only one brood of eggs is 

 produced, as the escape of the first brood must be effected by a rupture of the body wall. 



Genera of Uncertain Position. 



Genus DliplOl'Ms. 



(See Plate 8 figs. 9—19.) 



Provisionary Diagnosis. External body of adult red. 



Roots apparently absent; attachment to host by means of a tube running in the middle 

 line of the mesentery and opening into mantle cavity. 



