THE BEGINNINGS OF LIFE. 537 



extremely difficult to understand their universal dis- 

 tribution and co-existence in almost every tuft of 

 moss or lichen growing in all sorts of remote situa- 

 tions, seeing that no one has ever recognized amongst 

 filtrations or depositions from the atmosphere any 

 of the large eggs by which each of these forms 

 usually reproduce their like. The difficulty is, in- 

 deed, similar in kind, though very much greater 

 than that to which we have already referred in con- 

 nection with the development of the common edible 

 Mushroom in suitably prepared beds. The very small 

 size of the fungus-germs did afford a sort of excuse, 

 though this becomes wholly unavailable when we have 

 to do with the large eggs of Rotifers, Tardigrades, and 

 Nematoids 1 . Nobody pretends that these are universally 



1 See p. 433. It is also most important to note that Nematoids may 

 often be obtained at will and this almost as readily as Mushrooms by 

 a process which seems to be just as independent of ordinary eggs as the 

 other is of ordinary spores. I first learned about nine years ago from 

 some of the writings of Dr. Schneider (Miiller's ' Archiv.' 1858 and 1860) 

 that a form of free Nematoid, named by him Pelodytes, was generally to 

 be obtained by burying a few small pieces of flesh in a little damp earth. 

 Soon afterwards, whilst living at Broadmoor in Berkshire, I tried this 

 experiment having carefully examined the beef beforehand to see 

 whether it contained any encysted Nematoids or their ova. But having 

 found none, small portions of it were buried in a small quantity of earth 

 contained in a gallipot. The earth had been frequently examined 

 before without revealing a single Nematoid. After three weeks this 

 earth was found to be absolutely swarming with two kinds of Nema- 

 toids quite different from any forms which I had previously seen, 

 although I had been seeking them for more than two years previously 

 in all sorts of situations. 1 am, unfortunately, unable to say what were 

 the precise stages in the evolution of these Nematoids, since the mixture 



