402 Mr. G. C. Robson on the 



announced that part of the life-cycle of Schistosoma joponi- 

 cum was passed in the tissues of a Japanese fi-eshwater snail. 

 This snail was described by the present author (lo) as 

 Katayama nosophora, and a short account of the radula, shell, 

 and operculum was given. 



In May 1915 Pilsbry (9) referred this form to Blanfordia, 

 and in 1918 Annandale (2) placed the species in Heude's 

 Jlypsohia. There can be little doubt that the mollusc in 

 question should be referred to the genus described by Heude 

 under that name. 



As no complete account of the structure of this animal has 

 apparently been published, and the descriptions of Heude and 

 the present author were only slight and confined principally 

 to external features, it has been thought desirable to issue 

 some detailed account of its anatomy. In addition to its 

 role as intermediate host to Schistosoma japomcum and as a 

 member of a group of Mollusca the anatomy of which is very 

 little known, the discovery by Cort (4) of its powers of 

 resistance to dessication rendered the study of its respiratory 

 system an inviting subject. 



It is not the object of this paper to discuss the nomen- 

 clature of this group of Gastropoda, as the amount of informa- 

 tion upon the structure of E. Asiatic Paludestriyia-Vike 

 molluscs is too scanty to justify a taxonomic discussion. 



It is open to those interested in nomenclature to criticize 

 Pilsbry's reference of this form to Blanfordia or to inquire 

 whether Heude's genus should not be called Blanfordia; 

 but, until we have a general knowledge of the structure of all 

 the genera involved in this question, such discussions appear 

 a little premature. 



The publications of Bregenzer (3), Seibold (13), and the 

 present author (11, 12) serve to show that there are several 

 characters of fundamental importance which cannot be 

 neglected in the classification of the Paludesiritia-fovms ; and 

 it is very much to be regretted that in his admirable survey 

 of the freshwater Hydrobiidos of India (i) Dr. Annandale 

 should have ignored such characters as the nervous system 

 and female genitalia. 



The author is indebted to Dr. W. W. Cort, of the Johns 

 Hopkins University, for sending living examples of the snail 

 and for information concerning its mode of life. 



Structure. 

 I. Alimentary System. 

 The general disposition of the mouth and its adjacent area 



