Nucleus and Chromosomes 59 



A diflerent attack was tried by taking advantage of the fact that 

 colchicine coming in contact with egg cells in the second maturation 

 division would arrest the anaphase stage thereby creating a diploid 

 egg cell. If this cell imited with a haploid sperm, it could give rise 

 to a triploid individual. i-' The reasoning was logical enough and 

 colchicine coidd be introduced at the proper moment through the 

 admittance of sperm and colchicine by artificial insemination 

 methods. Whether sufficient dosage of drug was given shrouds these 

 tests with doubt. 



Experiments with frogs in 1947^^ encouraged the trial of introduc- 

 ing colchicine at the time of fertilization, since larvae from eggs 

 treated at fertilization seemed to be polyploid judging from the size 

 of cells and nucleus. The idea was extended to other animals, notably 

 rabbits and pigs.'*'^' ^^ Certain principles were substantiated by these 

 tests, viz., that the application of colchicine at the precise moment 

 of fertilization would bring triploidy in the zygote, because a 

 doubled egg cell would unite with a haploid sperm. 



Techniques were developed to inseminate artificially rabbits and 

 pigs,^^ by adding colchicine to sperm material. Proper concentrations 

 were determined by laboratory tests. Suspected triploid offspring were 

 studied cytologically and a conclusion was reached that egg cells were 

 doubled by this procedure. One rabbit that deviated from diploids 

 showed 66 chromosomes among certain mitotic cells of testicles. ^^ 

 There were other diploid cells in this test with 44 chromosomes. Thus 

 the individual may have started as a triploid zygote with reduction 

 as development proceeded. These results were, however, by no means 

 conclusive. Previous accounts as weU as these above have been criti- 

 cized and not without some basis. 



Similar experiments were done with pigs.^^- ^■'' Among 31 offspring 

 from artificial inseminations, one differed from the rest as well as 

 from dij)loid pigs. This male animal showed consistent mitotic fig- 

 ures with 47 chromosomes,*^^ a good triploid, that originated when a 

 diploid egg of 32 chromosomes and a haploid sperm carrying 15 

 chromosomes united. These techniques are new and merit fiuther 

 attention for theoretical studies of polyploidy among animals. ^'^ 



REFERENCES 



1. Barbir, H., and Callan, H. The effects of cold and colchicine on mitosis in the 

 newt. I'loc. Rov. Soc. London. B LS 1:258-71. \9\'S. 



2. Baricozzi, C. L'azione della colchicina sidla moitoio<;ia c sidla struituia dei 

 cromosoniie, studiata nelle cellule somatiche di Artemia salina Leach. Chromo- 

 soma. 2:293-307. 1942. 



3. , AND Fantom, L. L'azione della colchicina siil Nauplius ili Avtfinin 



salina Leach. Monit. /.ool. Ital. 53:69-74. 1942. 



