314 Mr. ^Y. NicoU on some 



birds and fishos, tlie Entozoan parasites of each species tend 

 to be alike in every country, there is no doubt that by reason 

 of unique local circumstances the parasites of a particular 

 host, or in some cases a particular parasite itself, are more 

 easy of study in one country than in anotlier. The same, of 

 course, applies to ditferent localities in the same country. 

 The presence of a rich invertebrate fauna, harbouring sporo- 

 cysts and cercaria^, and at the same time easy of access, is 

 beyond question a n;ost important aid in the study of the 

 adult parasi'es occurring in the vertebrate hosts. Besides 

 ensuring that in these liosts infection will be frequent, it 

 affords the means of studying the parasites throughout the 

 various stages of their development. Many places in this 

 country, and amongst them St. Andrews (where, owing to 

 the labours of Professor M'Intosh, the marine invertebrate 

 fauna is comparatively thoroughly known*), satisfy these 

 conditions, so that it is surprising that more labour has not 

 been expended on this subject. From the following notes, 

 which are in many cases the result of casual observation, it 

 will be evident that much research mio-ht, with a considerable 

 prospect of success, be devoted to the elucidation of the British 

 Trcmatode fauna. 



The hosts which I have had an opportunity of examining 

 are only such as occur with considerable frequency and are 

 commonly brought down by " caddies " or others out for a 

 day's shooting. The few fish noticed are some which have 

 died while in confinement in the tanks at the Laboratory. I 

 hope to be able to undertake a more extended study during 

 the ensuing months. 



The hosts with fheir respeclive parasites are as follows : — 



Larus ridibunchis. 



Echinostomum secundum, sp. n. 



Larus aryentatiis. 



Zeugorchis ncanthus, tren. et sp. n. 

 Echinostomum ."secundum. 

 Levinsenia .«imili?, Jayeiskiold. 

 Tocotrema lingua, Creplin. 



Hcematnjius ostralegus. 



Echinostomum secundum. 

 Levinsenia t-iinilis. 

 iJi.-tomum brevicolle, Creplin. 



minutum, Cohbold. 



Monostomum ignotum, sp. iuq. 



* Cf. e.(j. ' Marine Invertebrate Fauna and Fishes of St. Andrews/ 

 together with c any papers of note. 



