3/8 



SOUTH AFRICAN CERCARI.E. 



But I have never seen the appearance of redia formation in 

 any Pliysopsis ■africaiia harbruring Scliisfosnmuiii ]i(rmatohi\im. 

 The Japanese reported redia-formation in molhiscs infected with 

 the miracidia of Schistosomiiui japoiiciini, and recHcC, pn ducing 

 Schistosommn niansoni, are reported from Brazil. Leiper 

 described only sporocysts and daughter-spcrocysts as producino- 

 Schistosomiim Jucmatobium and Schistosomitm maiisoni in Egypt. 



Redi?e are quite easily seen with the naked eye, when the 

 liver-substance of an infested mollusc is macerated in water nn 

 a glass slide. 



If it can be demonstrated that the African species of Schisto- 

 sorno are sporocyst-prcduced, and never occur in rediae, we shall 

 have another means of differentiating the human parasites from 

 several cercarise which resemble them very closely. 



These results mav be tabulated thus : — 



EVR-SPOTTED CeRCART.E. 



Amphisfonics. Schistoso}nes. Distomcs. 



C. frondosa C. parvoculata C. fulvoculata. 



(Durban). (Durban). (Durban)- 



C. oculata. 

 (Durban). 



Other Cercarj.e. 

 Sell istosfl III cs. D iMoincs. 



S. ha?matobium (Durban, ]\rar- C. arcuata (Klerksdorp). 

 itzburg, Rustenburg, Magalies- C. comma (Muizenberg). 

 burg-, and Nijlstroom). C. cbscura (Alaritzburg). 



C. secobii (Maritzburg). C. catenata (Durban, Maga- 



C. gladii (Potchefstroom), liesburg, Klerksdor]). and 



Rustenl)urg ). 



The Rare Earth Metals. — ^Fany a striking instance 

 of the "practical" utility of research in pure science has been 

 furnished during the last two or three decades, but none more 

 apt than the gas mantle industry, which gives employment to 

 thousands of men, and finds profitable investment for millions of 

 money. A Finnish professor, Gadolin, while investigating in 1794 

 a mineral which had been found in a Swedish quarry near the 

 village of Ytterby, discovered a new metal, afterwards 

 called Yttrium, the first of a series of nearly twenty, 

 the oxides of whicli came to be generally known as the' rare 

 earths. For a century these seemed to have but little jM-actical 

 value, and few cAclop;cdias recorded the achievement, or even 

 the name of Gadolin, while the village of Ytterby remained 

 mimentioned in the gazetteers. Then it happened to occur to 

 von Welsbach to di]-) a piece of cotton into a solution of one of 



