278 A. RICHARDS. 



vesicles which by puncturing with the needle can be made to 

 collapse. 



From the work of many cytologists there has gradually ac- 

 cumulated a great mass of inferential evidence for chromosomal 

 continuity which is well known, and the general nature of which 

 was mentioned earlier in this paper. The form and size relations 

 of chromosomes, the behavior of the sex chromosomes, which 

 can be followed from one generation to the next, the homologous 

 character of somatic chromosomes, certain chromosomes not cor- 

 related with sex (according to the work reported by a number of in- 

 vestigators, e. g.,'by Wilson and by Carothers) , all of these facts can 

 be understood only with the greatest difficulty on any other basis 

 than that of continuity of structure. A very recent case is Wen- 

 rich's finding that in Phrynotettix there exists a pair, "B," whose 

 architecture is constant for all individuals studied, and another 

 pair, "A," which is recognizable " through all stages from sperma- 

 togonia to spermatids." This case is very clear and of great 

 importance. 



Vejdovsky's ingenious theory is of interest in relation to my 

 observations, although I do not find that the chromosome 

 behavior of Fundulus tallies with his descriptions of observations 

 upon which he bases his theory. He holds that the old chromo- 

 somes produce anlagen from which the new ones arise. As each 

 organic individual comes from the anlage in the female organs, 

 so do the chromosomes also arise from anlagen. The old chromo- 

 somes produce only anlagen for the new generation and the 

 formation of the latter sets in with the beginning of the new cell. 

 This anlage is the chromonema which gives rise to the two sub- 

 stances of which chromosomes consist, chromatin and linin. 

 Each chromosome begins its existence with a spiral chromatin 

 thread while the linin substrate of the old thread is lost to the 

 anlage of the "Kernenchylem." 



Reference must be made to the bearing of genetical work on 

 the doctrine of the significance of chromosomes. The results of 

 the great mass of recent work in this field demands as a practical 

 necessity that chromosomes be treated as if they are actually 

 persistent individuals, and the genetical behavior of heredity 

 characters is being steadily brought into line with chromosomal 



