Spindle and Cytoplasm 81 



somes settle to bottom.-^" Finally after all these characteristics are cited, 

 the fact remains that in colchicine-treated neuroblasts, the hyaline 

 globule increases when disorientation of chromosomes and spindle 

 destruction take place. Obscr\ations such as these support the idea 

 that, as colchicine acts, spindle structure becomes altered rather than 

 annihilated. 



The spindle fiber analyzed by electronic microscopy can be de- 

 scribed as compound, measuring from 600 to 800 A at the polar cap 

 stage.^^- AV'hen colchicine is applied to AUium root tip cells tor 30 

 minutes, the fibers lose their compactness. After one-hour exposures 

 the fibers are disoriented and fragmented. After 2 hours the fibers 

 api^ear swollen as well as increasingh fragmented, fn the untreated 

 cell, fibers remain as such regardless of the type, whether they be 

 chromosomal fibers, continuous fibers, or fibers of the polar cap stage. 

 With long exposure to dilute solutions or short exposure to stronger 

 concentrations, a decided swelling and a tendency to^vard "solubili- 

 zation" of their substance were apparent.''- 



3.5: The Arrested Metaphase and Spindle Mechanisms 



Interaction between colchicine and spindle fibers ultiniatelv de- 

 termines the arrested metaphase. The two types, oriented and un- 

 oriented,- both depend upon several \ariables existing during a treat- 

 ment or during a reco\ery from the drug. As mentioned before, con- 

 centration of colchicine, mitotic stage at time of action, length of ex- 

 posure, recovery processes, type of cell, and conditions favorable to 

 mitosis, all play an important role in the production of the particular 

 arrested metaphase, whether oriented or unoriented."'' 



A pattern such as the star metaphase (Fig. 3.1C) is far too regular 

 to be regarded \\holly as a random occurrence. During a reco\ery, 

 the star is characteristic, as is also the multiple star (Fig. 3. IF) . These 

 types do not reach a jjeak in a reco\ery until some time has elapsed 

 between application and the dissipation of drug. A majority of the 

 bipolar mitoses follow the star metaphases, thereby indicating that 

 reco\erv ^\•as nearing completion. Fhe star metaphases are the last 

 colchicine effects to ap)X'ar during recovery. The Triton material that 

 was fixed- directly out of colchicine and staine'd^ at three hours and 

 at succeeding intervals, shows that stars appear at once and build 

 u\) much faster than in TritunisJ'^ When the stars reach a jK'ak in 

 Triton, unoricntcd tvi)es, rather tlian bipolar mitoses, become the most 

 j)rominent mitotic figures. 



Any pattern, whether star or exploded metaphase, sliould be re- 

 garded as a response to colchicine, operating primarily through the 

 spindle fibers. Two basic comj>onents are accepted as established for 

 plants and animals; these are (1) continuous fibers and (2) rhromo- 



