ORIGIN OF THE ANIMATED TRIBES. 107 



set aside some other simple condition requisite for a non-ex- 

 ovo generation ? Who can tell what effect such exclusion of 

 air or such mode of admitting oxygen may have upon the 

 operation of the imponderables in the case ? To this I do not 

 believe that any satisfactory answer could be given. 



Perhaps the fashionable doctrine is in nothing placed in 

 greater difficulties than it is with regard to the entozoa, or 

 creatures which live within the bodies of others. These ani- 

 mals do, and apparently can, live nowhere else than in the 

 interior of other living bodies, where they generally take up 

 their abode in the viscera, but also sometimes in the cham- 

 bers of the eye, the interior of the brain, the serous sacs, and 

 other places having no communication from without. Some 

 are viviparous, others oviparous. Of the latter it cannot 

 reasonably be supposed that the ova ever pass through 

 the medium of the air, or through the blood-vessels, for they 

 are too heavy for the one transit, and too large for the other. 

 Of the former, it cannot be conceived how they pass into 

 young animals certainly not by communication from the 

 parent, for it has often been found that entozoa do not appear 

 in certain generations of a human family, and some of pecu- 

 liar and noted character have only appeared at rare intervals, 

 and in very extraordinary circumstances. A candid view of 

 the less popular doctrine, as to the origin of this humble form 

 of life, is taken by a distinguished living naturalist. " To 

 explain the beginning of these worms within the human body, 

 on the common doctrine that all created beings proceed from 

 their likes, or a primordial egg, is so difficult, that the mo- 

 derns have been driven to speculate, as our fathers did, on 

 their spontaneous birth; but they have received the hypo- 

 thesis with some modification. Thus it is not from putrefac- 

 tion or fermentation that the entozoa are born, for both of 

 these processes are rather fatal to their existence, but from the 

 aggregation and fit apposition of matter which is already or- 

 ganized, or has been thrown from organized surfaces. * * 

 Their origin in this manner is not more wonderful or more 

 inexplicable than that of many of the inferior animals from 

 sections of themselves. * * Particles of matter fitted by 



