445 MRS. H. L. M. PIXELI.-GOODRICH ON' 



Occurre:nCE of MixcuryrA in Chitox. 



During the last four or five years I have searched Chiton from 

 Plymouth and other parts of the British coast, as well as from 

 parts of the Pacific and Mediterranean, for traces of this parasite, 

 and it was only in October last that specimens of Chiton at 

 Plymouth were found to be strongly infected. The species of 

 Chiton so parasitised was CraspedocMlus cinereiis (Linn.)* from 

 Rum Bay, not Acanthochites [Chiton) fascicular is (Linn.), stated 

 by Labbc to be the host at Roscofl". In fact the latter species I 

 have never found to be infected. From this locality, out of 135 

 specimens of Craspedochilus cinereus examined, 85 have had a 

 more or less advanced infection. This proportion of infected 

 specimens, roughly two- thirds, does not coincide with Labbe's 

 description of Minchinia as a rare parasite. However, these figures 

 only refer to specimens of Craspedochilus cinereus fi'om a small 

 stretch of coast near Plymouth called Rum Bay. Perhaps the best 

 ground for the collection of Chiton in the Plymouth district is 

 the mouth of the river Yealm ; here, however, the specimens are 

 small only, and out of twenty-five not a single one has been found 

 to be infected with 3Iinchinia. Chiton (two only) examined from 

 Wembury Bay have also been free from infection. 



The infection is thus shown to be veiy localised ; whether the 

 Chiton in Rum Bay are suffering from an epidemic of this 

 parasite, or whether Minchinia is endemic to this locality, could 

 only be determined by an investigation extending over several 

 years. 



The parasites have so far only been recorded from the liver ; 

 they are, however, not restricted to this organ, but later overrun 

 all the connective tissue. They are especially numerous between 

 the lobes of the liver and the interior projections of the walls 

 of the so-called sugar-glands (Zuckerdriisen). Infection then 

 spreads to the wall of the gonad, radula sac, gills, and blood-spaces 

 in the foot. Cases of advanced infection can nearly always be 

 detected without dissection, because cysts full of spores can be 

 seen in the gills and through the epidermis of the foot. 



In such favourable positions, lying immersed in the host's blood, 

 the parasite has every opportunity of nourishing itself, and 

 during its rapid endogenous multiplication the liver becomes 

 gradually deprived of its reserve food materials. In early cases 

 of severe infection the presence of numerous colourless plasmodia 

 and young cysts gives a white appearance to the liver, which is 

 normally brownish. As the cysts become filled Avith brown 

 chitinous spores they appear black by reflected ligbt, and conse- 

 quently a liver with a severe infection at an advanced stage is 

 quite ijlack, as well as being enormously enlarged owing to the 

 bulk of parasites between the lobes. The liver-cells in such 



* [The parentheses around the names of authors placed after scientific names in 

 this paper are used in accordance with Article 23 of the International Rules of 

 Nomouclature (Proc. 7th Int. Cong. Boston, 1907, p, 14 (1912)).— Emtoe.] 



