ENTOZOA. 115 



of living animals. In no class of animals has the origin from equi- 

 vocal 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 Ligulee infesting pisci- 

 vorous 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 comfortable intestinal domicile into 

 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 inquire, 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 germs of Polygastria, 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 decomposi- 

 tion. Dr. Nelson* found that he could best observe the develop- 

 ment of the ova of the Ascaris mystax by placing the females entire in 

 spirit of turpentine for two or three weeks, at the end of which the 

 ovaries were found distended with ova containing young worms, not 

 only fully developed but alive, and endeavouring to rupture the 

 chorion by tightening the coils of their spiral and suddenly reversing 

 them. 



Mr. Bauer has recorded many experiments on the Vibrio tritici, 

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

 sation 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 

 resumed their living and active state. De Blainville states that the 

 Filaria papulosa 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 beyond 

 the known powers of endurance of the Rotifera, and which would 

 be truly surprising were not the simplicity of the organisation of the 



* XCI. 

 I 2 



