Embryonic Growth in Animals 205 



toxicity of colchicine, and has been described under various experi- 

 mental conditions and with other mitotic poisons. "^^ With less toxic 

 colchicine derivatives, spindle inactivation is apparent in a few horns. 

 Depending on the doses injected, recovery is possible, or considerable 

 cellular damage may be found. Binucleated spermatids may result 

 from the spermatogonia! mitoses during recovery assuming the "dis- 

 tributed" type with two nearly equal groups of chromosomes (cf. 

 Chapter 2) . 



In fowls also, colchicine may induce severe degenerative changes 

 in testicular cells. These are followed by regeneration seven days 

 later.17 



No polyploid spermatozoa have been reported in vertebrates. On 

 the contrary, in the insect Triatomn infestans (order: Hemiptera) , 

 colchicine not only inhibits the spindle function, but as a consequence, 

 modifies considerably the size of the spermatids (Fig. 8.1) . This is 

 observed after nine days, wlien all spermatogenetic cells have dis- 

 appeared. The simple numerical relations between nuclear sizes are 

 a strong evidence in favor of polyploidy, although the exact inter- 

 pretation of these facts awaits further research. ^^ 



Control 



Colchicine 9 days 



420 842 1677 



3073 



Fig. 8.1 — Action of a prolonged treatment by colchicine on the nuclear diameters of 

 the spermatids, expressed in conventional units, in Triatoma infestans. Several categories 

 of polyploid nuclei with diameters in the relation 2,4,8,16. (After Schreiber and Pelle- 



grino'"') 



