Limitations of the Cell Theory. 77 



as recapitulation, adaptation, inheritance, and distribution. The 

 first class of characters are (as already expressed in Chapter II.) 

 cell-characters, which have arisen through mutations, are repre- 

 sented in every cell of the organism, and are usually inherited as 

 distinct units. Since they arise in and are carried by the nuclei 

 they may be called karyogenetic. To the second category 

 belong characters which arise gradually in the organism through 

 impact of the environment or through " orthogenesis," * may apply 

 only to localized portions in the life-cycle of the organism, and at 

 first are not incorporated in the germplasm. Such characters we 

 may call organismal 2 , in contradistinction to cell-characters. 

 Organismal characters may imply an increase in the length of the 

 life-cycle, as strikingly evidenced in so many animal larvae which 

 undergo metamorphosis, or they may show stages in shortening, as 

 in the gametophytes of many higher plants. 



The attitude of experimental biologists to the questions of 

 recapitulation and inheritance of acquired characters (although the 

 former has never fallen into the same disrepute as v the latter) has 

 been generally one of skepticism and denial. Reasons for adopting 

 a different position may be given as follows: (1) the difficulty of 

 explaining adequately the abundant facts of recapitulation in plants 

 and animals by means of mutations or changes originally germinal; 

 (2) the logical necessity of the principle of functional inheritance in 

 some form to explain the origin of embryonic recapitulatory 

 characters involving adaptation ; (3) the approach to an under- 

 standing, through such agencies as hormones and enzymes, of how 

 the transmission and ultimate germinal fixation of somatic modifi- 

 cations may take place ; (4) the slowly accumulating direct 

 experimental evidence for parallel induction and the transmission 

 of modifications. 



In contrasting organismal with cell characters we are con- 

 trasting two points of view regarding the organism which are at 

 least as old as Aristotle and Empedocles. Modern representatives 

 of these views speak of the organism as a whole on the one hand, 

 and of elementalist or particulate theories on the other. It scarcely 

 needs pointing out that elementalist conceptions, particularly of 



' An orthogenetic result may also of course arise from a succession of 

 germinal changes or mutations following each other in any line of phytogeny. 



* In the Linnean discussion, Professor F. E. Weiss suggested the obvious 

 antonym cytogenetic for this category of characters, since they are apparently 

 cytoplasmic in origin. This term had already been considered, but was finally 

 discarded because "organismal " expressed better the idea desired. Never- 

 theless it will be a useful term in certain connections. 



