272 Bud-sports [CH. 



differences prove both too little and too much. I cannot 

 but believe that all this evidence points to the conclusion 

 that we are about to find among the chromosomes one more 

 illustration of the paradoxical incidence of specific difference, 

 not the fundamental phenomena on which that difference 

 depends. Among coleopterists punctulation is sometimes 

 a feature of great systematic importance. To dipterists 

 neuration and chaetotaxy sometimes give useful critical 

 data. In certain orders of Lepidoptera, the Hesperidae, for 

 example, the structure of the gonapophyses sharply dis- 

 tinguishes the species where all outward tests fail. But 

 proceeding farther with each of these criteria, we are sure 

 to come upon other groups where for a long series of 

 diverse types the critical feature, so important elsewhere, 

 may show no differences, or, on the contrary, may show 

 marked instability. 



There remains the suggestive fact that all that has been 

 witnessed regarding the behaviour of the chromosomes is 

 in fair harmony with the expectations which our Mendelian 

 experience would lead us to form respecting the hypothetical 

 " bearers " of varietal differences*. On the other hand, with 

 one striking exception, nobody has been able to connect 

 a cytological difference with a character-difference in any 

 instance. The exception, of course, is the case of the 

 accessory chromosome which the researches, especially of 

 Wilson and Morgan, have proved to be definitely connected 

 with the development of femaleness (see p. 188). 



The Case of Bud-sports. 



There is another circumstance which must be taken 

 into account in any attempt to see the facts of segregation 

 in proper relation to other biological phenomena. This is 

 the obvious fact that when a bud-sport occurs on a plant, 

 the difference between the sport and the plant which pro- 

 duced it may be exactly that which in the case of a seminal 

 variety is proved to depend on allelomorphism. This subject 

 may best be discussed in reference to a practical illustration. 

 All naturalists remember the passage in Animals and Plants 



* The recent work of Godlewski gives however strong reason to believe 

 that heredity in Echini may be governed by the cytoplasm of the egg. 



