ENTOZOA. 79 



egg-membrane^ assimilates the remaining vitelline mass, and is soon 

 strong enough to burst its prison, and commence its independent 

 career of existence. 



The Entozoa are hardly less remarkable for their tenacity of life 

 and revival from a state of apparent death than the Infusoria, and 

 the knowledge of this property is indispensable to a fair estima- 

 tion of the chances of the re-introduction of the ova of Entozoa 

 into the bodies of living animals. In no class of animals has the 

 origin from equivocal generation been more strenuously contended 

 for than in regard to the Entozoa. The great entozoologists 

 Rudolphi and Bremser were advocates of this doctrine; and Bremser 

 did not scruple to charge the Berlin professor with a physiological 

 heresy, when he ventured to account for the high organisation of 

 certain Ligulse infesting piscivorous birds, by the hypothesis that they 

 had been developed from the lower grade which they previously 

 exhibited in the cold-blooded fishes swallowed by the birds, through 

 the stimulus of the heat and nutritious secretions of the more com- 

 fortable intestinal domicile to which they had thus been accidentally 

 introduced. 



The advocates for the equivocal generation of the Entozoa adduce 

 the fact that herbivorous mammals are not less subject to Entozoa 

 than carnivorous ones : and how, they enquire, could the ova of 

 Entozoa be preserved in the water that serves as the drink of such 

 animals ? Or how, having become dried in the air, could such ova 

 afterwards resume the requisite vitality for embryonic development ? 

 We may admit that the ova of Entozoa could not, like the much 

 more minute ova of Pologastria, remain suspended in the atmosphere, 

 since they are specifically heavier than water ; but, with respect to 

 their powers of retaining dormant life, we have sufficient analogical 

 evidence to reject the assumption that they soon fall into decompo- 

 sition. 



Mr. Bauer * has recorded many experiments on the Vibrio tritici^ 

 or parasite of wheat, a minute worm possessing the essential organis- 

 ation of the Nematoidea, not less remarkable in their results than 

 those of Spalanzani on the Rotifer : the Vibriones were dried, and 

 when re-moistened, after the lapse of four to seven years, they re- 

 sumed their living and active state. Dr. Biainville states that the 

 Filaria papillosa revives from a similar state of torpidity produced 

 by desiccation. 



It has been proved that the mature Entozoa will resist the effects 

 of destructive agents, as extremes of heat and cold, to a degree 



* Philos. Trans. 1823, p. 1. 



