THE BEGINNINGS OF LIFE. 433 



Itzigsohn, and many others l . And, moreover, it is 

 stated by the Rev. M. J. Berkeley that the common 

 edible Mushroom is cultivated by gardeners with as 

 much certainty as any other vegetable, although no 

 seeds are ever sown. It is only necessary that beds 

 should be prepared in a certain fashion, and then this 

 complex Agaric almost infallibly appears. Mr. Berkeley 

 says the process is c so certain, that no one ever saw any 

 other kind of Agaricus produced in mushroom-beds ex- 

 cept a few of the dunghill tribe, where raw dung has been 

 placed near the surface of the bed ;' and he adds, c this 

 could not happen if the mushroom sprang from seeds or 

 sporules floating in the air, as in that case many species 

 would necessarily be mixed together 2 .' These facts are 

 almost inexplicable unless we resort to the belief that 

 the lower forms of Fungi may arise by heterogenesis 3 , 



1 See Appendix D, pp. liii-lix. 



2 It will afterwards be seen that almost precisely analogous facts have 

 to be recorded concerning the appearance of Nematoids in prepared 

 mixtures (p. 537), and the same difficulty as that which Mr. Berkeley 

 experienced with regard to the derivation of Mushrooms from atmo- 

 spheric germs is applicable to the origin of the germs of the Rotifers, 

 Tardigrades, and Nematoids, which are always to be found in tufts of 

 Moss and Lichen. 



3 After quoting Fries's objection to this view, on the score that the 

 small size and infinite number of the sporules of Fungi permitted of their 

 being widely disseminated through the air, the Rev. M. J. Berkeley very 

 fairly remarks (Lindley's Veget. Kingdom,' p. 34) : ' I give his words 

 as nearly as possible, because they may be considered the sum of all that 

 has to be urged against the doctrine of equivocal generation in Fungi ; 

 but without admitting, by any means, so much force in his statement as 

 is required to set the question at rest. In short, it is no answer to such 

 arguments an those just adverted to.' 



VOL. II. F f 



