OR EQUIVOCAL GENERATION. 367 



Bar's observations were, but Mr. Metford seems not to have 

 paid any attention to them ; for at the conclusion of his essay 

 upon the origin o( Entozoa, in your last volume, (p. 204,) after 

 proving the fallacy of the different hypotheses that have been 

 assumed to account for their origin, he says, " The reader is, 

 I doubt not, by this time sensible of the great difficulties with 

 which this problem is beset; and must perceive that if my 

 position be true, viz. that worms do not gain access to animals 

 by the mucous cavities, nor are they transmitted by the parent 

 to their young, that the doctrine of spontaneous generation is 

 inevitable. But as this is a doctrine inconsistent toith reason 

 and analogy, the question, as I before hinted, must be left sub 

 judice until future facts and observations shall discover the 

 truth;" thus, after he had exposed the false positions they had 

 assumed, he, notwithstanding, hesitated not in the least to 

 declare his firm opinion against equivocal generation. 



Burmeister has laid himself open to the above observation 

 of proving too much, in the last quotation I made from him: in 

 the preceding section, (§ 202,) he assumes the principle, "that 

 from nothing, nothing can be produced." We may also assume, 

 without fear of contradiction, the converse principle expressed 

 in the common proverb, " like produces like ;" if, therefore, 

 " the skin has precisely the same structure as the mucous 

 membrane of the intestinal canal," how comes it to pass that if 

 we admit equivocal generation, it does not produce the same 

 parasites ? why should they be in one situation Insecta, and in 

 the other Vermes? Certainly the same structure must of ne- 

 cessity produce the same forms upon the germs that are 

 excreted from it. It would, I doubt not, puzzle the most ardent 

 advocate of the doctrine, to give a satisfactory solution to the 

 above query. If "the universally distributed organizable matter" 

 is the parent of the germs, (admitting, for argument, that it is 

 endued with the principle of vitality,) it must likewise produce 

 the same forms wherever it is situated, or otherwise we must 

 admit as many sorts of organizable matter as species of para- 

 sites, both external and internal. With regard to the supposed 

 transformation of the intestinal flocks into intestinal worms, 

 do we not know that every part that is separated externally 

 from any of the higher or more fully developed organized 

 beings, (be it remembered he is treating of man, the highest 

 organized being,) dies the instant that it is severed from the 



