DEVELOPMENT 211 



of Morganism are essentially similar, in some important respects, 

 to those of Weismannism and, of course, that was their inspiration. 

 We must regard Morgan's genes as expressing the same essential 

 idea as the determinants of Weismann. Like the latter, they are 

 located in the chromosomes although they are too minute to be 

 visible. Cruder views regard them as physical-chemical in nature 

 though the less naive writers refer to them as the " carriers of 

 hereditary qualities." It is said that something like rows of genes 

 may be seen in the nuclei of cells undergoing maturation and 

 there are appearances, in these changes, that suggest the joinings, 

 disjoinings, reassortments, etc., of the genes. This is true, but 

 it must be noted that different interpretations of the appear- 

 ances have been made and that there is not general agreement 

 among cytologists as to what actually occurs in the maturing 

 germ-cells. 



And it is expressly stated by Morgan that his hypothesis is 

 not one of development, mainly because the processes of organo- 

 geny and histogenesis are not accompanied by any nuclear 

 phenomena that can be associated with differentiation. Neverthe- 

 less, modern genetics does maintain that there is a correlation 

 between phenomena that include joinings, assortments, etc., of 

 the genes and the appearances in later individual life-histories 

 of morphological characters and, to that extent, Morganism must 

 be a hypothesis of development. 



And it is to be noted that it is a morphological hypothesis 

 and that, in some quarters, it is held to be the line along which 

 (as in the past) the study of transformism and, therefore, the study 

 of the evolutionary career must proceed. It implies little of what 

 we may strictly call experimental investigation, though that is 

 beginning and may be expected soon to reconstruct the hypo- 

 thesis. In the sections that follow we shall further examine into 

 its bases. 



75. ON THE DEVELOPMENTAL ORGANIZATION 

 By this term we mean that which is involved in the development 

 of the differentiated adult organism from the relatively undiffer- 

 entiated ovum, spore, bud, etc. We shall endeavour to state with 

 as little resort to hypothesis as possible, what the developmental 

 organization appears to be. 



