CHAP, xviii A "FAIRY TALE OF SCIENCE"? 221 



By a fuller consideration of the problems of atavism, 

 and by a growing hesitation to admit the inheritance of 

 acquired qualities, doctrines of the continuity of the 

 germ plasm have gained in popularity and acceptance. 

 There are difficulties about the facts. In certain 

 animals it appears that, at a very early stage in 

 embryonic development, part of the segmented ovum 

 is differentiated for reproductive purposes. Here then 

 the parental germ may be styled continuous with the 

 germs which are a preparing in the reproductive tissues 

 of the growing embryo. But in most cases it is a long 

 time before we reach specialised reproductive cells. 

 The germ cells seem to be derived, if only at this early 

 stage in development, from somatic cells, and continuity 

 with the past seems to be disproved in favour of 

 reciprocity in the present. At this point, therefore, 

 Weismann and others take a deeper plunge into sub- 

 microscopic minuteness and unverifiable theory. They 

 cannot prove continuity of germ cells, but nothing can 

 hinder their asserting continuity of germ plasm or the 

 like, i.e. continuity of the invisible substance, believed 

 to form part of the contents of [reproductive] cell nuclei, 

 and to be the vehicle of hereditary qualities. 1 On this 

 view of things we must alter our parable. The owl 

 comes from the egg true ; but the egg (the microscopic 

 living embryonic ovum) never came from the owl 

 never ; the owl came from the egg, and the egg came 

 from the egg. The living hereditary substance, the 

 assumed carrier of the qualities of heredity, is called 

 by Galton " Stirp." Weismann calls it " Germ plasm," 

 subsequently " Idioplasm," and later on introduces 



1 The phrase (in the allied form, " continuity of the germ proto- 

 plasm. ") is not of Weismann's coinage, but goes back to a previous writer, 

 Jaeger. 



