158 ROBERT T. HANCE. 



The retention of chromosome identity or individuality in the 

 culture raised cells is also obvious. Fig. 5 shows a series arranged 



P 1 PT II r i i i 



( 



FIG. 5. Camera lucida drawings of the longer chromosomes of the chick 

 complex arranged according to length. 

 Top row from sectioned embryo. 

 Lower row from tissue culture cell. 



according to length, of the longer chromosomes of the mitotic 

 complexes from cells found in a sectioned embryo and in a 

 tissue culture. The smaller chromosomes of each cell have been 

 omitted for convenience in printing and because, being short 

 rods, they show no easily distinguishable features. A slight 

 variation between the two sets of chromosomes illustrated enters 

 through it being impossible, as pointed out above, to find a polar 

 view of a metaphase plate in tissue culture cells. The lower 

 series of chromosomes is taken from a very late prophase (tissue 

 culture), so late that many of the chromosomes have assumed 

 characteristic form. Number (from left to right) 3 has not yet 

 taken on its final form. With this exception in mind it can be 

 seen that the form of corresponding chromosomes in the two 

 series and that the comparative size relations of a given chromo- 

 some to others in the same series or in the other series are identical. 

 The possible causes for the chromosomes of the culture cells 

 being larger have been discussed above. 



It is possible then to conclude that tissue cultures, as far as 

 the mitotic phenomena are concerned, are quite normal and 

 differ from these processes in the body only in minor reactions 

 to the physical limitations of their surroundings. 



