CS Uv. W. Nicoll on the 



bnbalis. From their observations no parasite appears to 

 infest the fish liaiinting the pools and crevices alonji; tlie 

 shore in the same way as Podocotijle atomon, Uiid., has been 

 found to do at St. Andrews. The preseuce of this Trematodc 

 is quite a feature ; it occurs in cigiit out of the nine species 

 examined. Another common form is Echiiioi'hi/nc/ins acus, 

 Kud., which was found in four species. Amongst the fishes 

 from (keeper waters tlic widely-spread Ilemiurus forms and 

 Dcror/cncs variciis, ^liiller, arc recorded very frequently l)y 

 both the above-mentioned obs.u'vcrs. As might luive been 

 expected, the same is true in the present instance. 



Fish, such as the herring and haddock, which roam far aud 

 wide in their search after food tend to exhibit the same para- 

 sitic fauna in whatever quarter they are taken, but the littoral 

 fish, with their more circumscribed lives, are dependent on 

 local faunie for food, and in couscqueuee their parasites vary 

 according to the locality. 



A case like that of Podocotijle atomon, Rud., would almost 

 lead one to enunciate the hypothesis that the Entozoa of a 

 particular fish depend moi'e on its environment than on the 

 species to which it belongs ; that is to say, that no matter 

 what t!ie species of fish the parasites found in it ought to be 

 the same as tho>e found in otlier species from the same 

 neighbourhood. This raises the very important question of 

 idiosyncrasies in feeding, for it is well known that ditfereut 

 species, although living quite close together, have often 

 entirely different moles of feeding. Van Beneden took some 

 pains to note the food of the various fish which he examined; 

 but into this matter I do not propose at present to enter. One 

 case, however, that of the shanny, Blenn'ws pJiolls, cannot be 

 overlooked. It occurs here commonly, and 1 had an oppor- 

 tunity of examining a large number, but in no instance did 

 a single parasite pre>ent itself. Such a fact is not remark- 

 able in itself, but, in view of the frequency with which other 

 fish in the vicinity were infected, it is striking enough. 

 A'an Beneden found tlie food of the shanny to consist of 

 crustaceans, Balanus for the most part. In addition to 

 crustaceans I iiave met with excessive numbers of small 

 gastropods, especially young Littorlna. Tlius the food is 

 apparently not so very dificrcnt from that of other species. 

 The presence of the large number of shells in the intestine 

 might bti oflered as a reason for the absence of parasites, 

 but shells and other hard debiis are found in fish in which 

 parasites abound. Another explanation might be sought in 

 some constitutional peculiarity of the shanny which renders 

 it an unsuitable host. Similar instances — c. g. Agonus 



