390 ON THE ORIGIN OF ENTOZOA 



them. Some authors deny the presence of worms in the small 

 birds, even in the Passeres ; but this opinion is founded on 

 imperfect observations, for at least three species of worms 

 have been detected in the nightingale {MotacUla Ltiscinicif. 

 In swallows I have found them also, and in the sparrow and 

 others. It cannot be doubted that the domesticated birds 

 labour under worms to a great extent, particularly those reared 

 in cities, and that are crammed : those who range freely in the 

 country, and that are in good health, are less troubled with 

 them ; yet aquatic birds abound in worms. As far as regards 

 tish, it is entirely false that the migratory ones nourish more 

 of them than others ; for during many years of careful examin- 

 ation of Harengiis and Salaris, Rudolphi never found a larger 

 number in them than in the non-migratory kinds. It, after all, 

 depends mostly upon the nature of the food and the season of 

 the year ; thus the pike {Esox Lucius) sometimes abound in 

 worms, at others are destitute of them ; so fishes that take in 

 quantities of sand in their attempts to gorge large objects, as 

 has been seen in the sturgeon (^Acripenser sturiu) in parti- 

 cular, and in those whose stomachs and intestines are replete 

 with the debris of hard shells, as may be often seen in the 

 Pleuronectes, are often free from them. 



The explanation of the fact, that whole families are often 

 simultaneously afflicted with, or are free from worms, is not 

 difficult ; for the most part they all partake of the same kind of 

 food or drink, whether that be bad or good, by which the 

 verminous diathesis is increased or diminished ; and the case 

 mentioned by Goeze of a family, in Brunswick, being all of 

 them (two servants excepted) afflicted with the Lumbric worm, 

 admits of a similar explanation, for the latter were probably 

 furnished with more robust constitutions, indulged in spirits, or 

 were, in some way or other, protected from the bad influence 

 of the common fare. 



The second argument is by no means favourable to the 

 doctrine supported by Pallas, viz. that certain species of 

 worms infest particular species of animals, and are not to be 

 met with promiscuously in every species ; for if the ovules 

 are diffused through the atmosphere, or are floating in the 



« Monostoma ventricosum, in tlie liver ; Distoma mavrosianiuni, in the recUim ; 

 Tania platycephala, in the small intestines. 



