262 BERTRAM G. SMITH. 



of the body of the child may receive from each parent not only 

 half of its chromatin substance, but one half of its chromosomes, 

 as distinct and individual descendants of those of its parents ' 

 (Wilson, 1900). 



Boveri (1909) found in Ascaris that in sister cells preparing for 

 division the configuration of the groups of chromosomes is the 

 same. The similarity of the sister cells is explicable on the view 

 that the chromosomes retain during the resting stage the same 

 shape and size and relative location that they had at the end 

 of the preceding division. In cells of these same embryos that 

 are not sister cells, a great variety of arrangements of the chromo- 

 somes is found, and no two arrangements are so nearly alike as 

 are those found in sister cells. 



Other evidence for the continuity of individual chromosomes 

 is derived from those cases where the reconstruction of the resting 

 nucleus takes place through the metamorphosis of each chromo- 

 some into a hollow vesicle, and the aggregation or fusion of these 

 chromosomal vesicles to form a single nucleus. Such, to be sure, 

 is not the only type of telophase (Wilson, 1900, p. 71), but it 

 takes place in many segmenting ova and in some spermatogonia. 

 According to Conklin (1902), in the late stages of mitosis of the 

 segmenting egg of Crepidula the chromosomes enlarge to form 

 vesicles and these unite into a resting nucleus; the nuclear 

 membrane is composed of the outer walls of the vesicles, while the 

 inner walls stretch through the nucleus as chromatic partitions; 

 the chromosomal vesicles from the egg and sperm nuclei respec- 

 tively remain distinct longer than those from the same germ 

 nucleus. Vesicular chromosomes have been described in fish 

 eggs by Moenckhaus; the individual vesicles fuse with their 

 neighbors and these larger ones with each other until at last the 

 entire nucleus is simply one great -vesicle, which is at first lobed, 

 but later is well rounded. Wenrich (1916) says of Phrynotettix: 

 'The spermatogonial divisions showed that each chromosome 

 forms a sac or vesicle in the earlier telophases, and that it expands 

 and becomes diffused within these vesicles; that, although the 

 vesicles appeared to coalesce, there is always a remnant of each 

 chromosome visible in the center of the region occupied by the 



