THEORY OF INHERITANCE. 27 



migration was disproved. The eggs which are extruded with the 

 faeces are, as far as the intestinal worm is concerned, lost, though 

 they may serve as food for other animals (Goze). It was certainly 

 astonishing that by far the greater number of eggs should incur this 

 fate, but even this fact was brought into accordance with the theory. 

 It was asserted that the intestinal worms, which could not, like other 

 animals, deposit their eggs in a chosen place, must leave it to chance 

 whether they passed into the blood-vessels or not ; and furthermore, 

 that the probability of such a haphazard transference was far less 

 than that they should be extruded from the body before it could take 

 place (Bloch). 



That this view, under the influence of that theory of evolution 

 which was then dominant, degenerated into wonderful subtleties and 

 refinements in many of its supporters, must not be considered as due to 

 the theory itself ; x but in other respects it shows so many weak 

 points, that it seems hardly necessary to refute it by calling to mind 

 the various worm-epidemics (sheep-cough, liver rot, &c.), or the Ccenurus 

 that almost invariably kills its host, and generally before it arrives at 

 sexual maturity. The influences, however, which led to this opinion 

 are not difficult to understand. On the one hand was the undeniable 

 fact of the sexuality of the Entozoa and their striking fertility ; on the 

 other, the difficulty, apparently even impossibility, of tracing the origin 

 of these animals to the eggs extruded with the fasces. The idea of 

 hereditary transmission seemed to afford a way out of this dilemma, and 

 appeared all the more feasible, seeing that many observers stated that 

 they had found Entozoa not only in the young of animals, but even in 

 the embryo within the body of the mother. "Whether the cases here 

 alleged were reliable or not, 2 is a matter of indifference to us, but it 

 is surprising, and hardly agrees with this theory of inheritance, that 

 these cases were extremely few in number. It was, accordingly, hardly 

 unjustifiable in Pallas to use not only the directly transmitted eggs, 

 but also those evacuated from the body, to explain entoparasitism. 

 He did not succeed, however, in proving his opinions by direct experi- 

 ment, any more than his illustrious contemporary, van Doeveren,* 

 who also endeavoured to explain the distribution of Entozoa by the 

 theory of the transference of similar germs, but we must not forget to 

 pay our acknowledgment to the clear and accurate perceptions of 

 this great naturalist. Entozoa do actually originate, as we now 



1 According to Eberhard's " Neue Apologie des Socrates" (Th. ii., p. 333), the parasites 

 were present as eggs during the age of innocence, but were hatched after the Fall. 



2 For a list of these cases see Bloch, loc. cit., p. 38 ; also Davaine, " Traite des 

 Entozoaires," 2me ed., p. 11 : Paris, 1877. 



3 " Abhandlung von den WUrmern in den Gedarmen des menschlichen Kbrpers," p. 

 106 : Leipzig, 1776. 



