THE BEGINNINGS OF LIFE. 535 



mena. But a much more marked discrepancy between 

 facts and generally received theories exists in refe- 

 rence to other phenomena. Thus, when speaking of 

 Rotifers, Pritchard says, in his "^ Infusoria' (p. 6^^\ 

 <^One remarkable circumstance must be borne in 

 mind by the animalcule hunter. If he happens to 

 remember a pond where some rare species abounded 

 last year, let him not again turn thither in search 

 of it, as the chances will not be in his favour. 

 These creatures rarely exist in the same water during 

 two successive years. The reasons for this are not 

 easily ascertainable. The remark is equally applicable 

 to Volvox and the Desmidise. The search will be most 

 productive if prosecuted on new ground.' Now this 

 variability in the habitat of the rarer kinds of Infusoria, 

 incompatible as it is with received notions concerning 

 *^ winter-eggs ' and <^ resting-spores,' is thoroughly har- 

 monious with all that we have said concerning the 

 life-history of many of these forms and the extreme 

 variability at different times in the products of hetero- 

 genetic transformation— peculiarities which were long 

 ago dwelt upon by Dr. Gros. 



Again, the extreme prevalence and almost universal 

 distribution of certain common forms of Rotifers, Tar- 

 digrades,and Nematoidsi,will become quite inexplicable 

 to those who disbelieve in the occurrence of hetero- 

 genetic transformations— in the face of our present 



^ Each of these three forms of hfe having the peculiarity that they 

 multiply their kind by notably large gemmae or eggs. 



