OR EQUIVOCAL GENERATION. 373 



perhaps he might urge that the milk of which the cheese is 

 made is an animal secretion. But what can be urged in the 

 case of mites found in the mould of gardens under flower-pots, 

 &c. The mould is not an animal secretion ; if, therefore, several 

 species of Acari do not originate equivocally, why should one 

 species of the same genus have a spontaneous origin given 

 to it? 



Burmeister also says, respecting unimpregnated females being 

 fruitful, that it perfectly proves the possibility of spontaneous 

 development: this I positively deny. Equivocal generation 

 means, according to the instances cited by Burmeister, that the 

 secretions of one type of beings produce a germ, and that 

 germ in its development produces a being of a different type, 

 (the secretions of man, for instance, producing worms, mites, 

 and lice.) Now, in what respects does the generation of the 

 Aphides resemble this or any of the exceptions to the general 

 law mentioned by him ? (upon some of which he casts well- 

 founded doubts.) Do they not produce the very same typical 

 beings? The same principle I laid down at first — "like produces 

 like " — is most strictly adhered to : a parent of the same type 

 is invariably required. When was an aphis, moth or bee c ever 

 observed to produce the germs of any other insect ? Does not, 

 in every instance which he quotes, the unimpregnated female lay 

 eggs which produce the same species ? The eggs were laid ac- 

 cording to the regular course of nature, in the very same manner 

 in which impregnated ones were laid : they sprung not from 

 external secretions, but from the proper oviduct of the insect ; 

 so that, so far from supporting spontaneous generation, they 

 point directly contrary. There are organs whose sole function 

 is the secreting of germs : and the germs produced by those 

 secretory powers in their full development, produce the same 

 typical beings; the only difference being in the non-impreg- 

 nation by the male, which takes place regularly in one family ; 

 being in fact their regular mode of propagation : the common 

 sexual generation of other insects being their exception— not 

 their rule. But it appears that when the fruitfulness of the 

 females is exhausted by exposure to cold, or what other cause 



c Burmeister, or his translator, has made a ludicrous error at the bottom of 

 page 312, where he speaks of a queen-bee laying unfruitful eggs, which produced 

 fruitful females. 



NO. IV. VOL. IV. 3 C 



