Dublin Review S.R.B. One B 



)-N the shifting condition of biological theories it is, 

 )-perhaps, not to be wondered at that a constant stream 

 of what are sometimes called, without any offensive mean- 

 ing, " works of vulgarization " should issue from the press. 

 If all were as sane, as well-informed and as agreeably set 

 forth as that of Mr Walker (Hereditary Characters and 

 their Modes of Transmission. London. Edwin Arnold. 

 1910. 8s. net) certainly we should ha\e nothing to 

 grumble at nor any other attitude of mind than that of 

 welcome for them. 1 1 



From the numerous points which are dealt with in this 

 book three may be selected to exhibit the shifting nature 

 of scientific theory as above alluded to. It is well known 

 that but a few years ago the view was widely held that the 

 chromatin of the sex-cells was the bearer of the hereditary 

 characteristics (Nageli's idioplasm). Now, as Mr Walker 

 points out, it seems quite likely that the linin (another 

 constituent of the cell) may be its really permanent con- 

 stituent and that chromatin may be no more than a mere 

 secretion or excretion of the linin. If this be so, the whole 

 theory of those who see in the chromatin the transmitter 

 of hereditary characters -naturally falls to the ground. 



The theory of mutations put forward by de Vries 

 some years ago receives careful attention at Mr Walker's 

 hands and further illustrates the point to which we have 

 been alluding. The essential feature of de Vries' theory is 

 that minute modifications, so much relied upon by Darwin 

 as the producers of variation, have little or no share in that 

 process but constantly fluctuate around a mean, the real 

 things which count being sudden and considerable 

 changes or " mutations." This thesis was mainly sup- 

 ported by his observations on Oenothera lamarckiana, the 

 evening primrose. Boulanger's observations on the same 

 form which, by the way, suffers from the^bubt tnat 

 exists as to whether it is really a wild SDg<^s~ajf( not an 

 artificial cross published in the JournM ft. Botqny, seem 

 to point to quite different conclusions tjwpose reached by 

 de Vries. Many other difficulties exist riTOnexip/ii with 

 this theory, and Mr Walker goes so far as>ro>^mt " we 

 are then driven to the conclusion that, xvna^fever the 

 results of mutations may be, they are not usually the 

 ~,-, n j^x-^rl nf evolution." Others having shown, with 



