382 Colchicine 



viously been reported in a short note.-" A frog sperm suspension with 

 2.6 X 10~* M colchicine was most toxic to eggs, and only 8 per cent 

 of these developed normally. It has been claimed that this did not 

 result from a direct action of the alkaloid on the eggs at fertilization.^^ 

 The production of triploidy deserves close attention."*-- •^•'' ^' A sur- 

 prising fact is that the rabbits and pigs were considered to have an 

 abnormal growth with increased Aveight and size. In the first papers, 

 triploidy was deduced from the increased size of red blood cells and 

 spermatocyte heads. The accuracy and significance of these measures 

 have been severely criticized.** However, chromosome counts were 

 later published. In frogs, tetraploid, but also diploid, triploid, and 

 pentaploid cells Avere found.^e In rabbits, a considerable variation of 

 chromosome number was found. While the diploid one was the most 

 frequent, it is clear from the results published that the animals were 

 heteroploid.46 The same applies to the single triploid pig. While in 

 a preliminary note about this animal it was claimed that the mitotic 

 count in the testicle was "certainly over 45 and not more than 48," 

 and that the animal resulted from the fusion of a spermatozoon with 

 15 chromosomes ("Old Swedish" race) and an egg with a doubled 

 chromosome complement of 32 (mixed race) , the results of a later 

 publication are by no means so clear.'***- ^^ 



It is already evident that in producing artificial "polyploids" one 

 should deal with animals with a well-known number of chromosomes 

 and should not cross two varieties with different and imperfectly 

 knoA\n numbers.3 The detailed stud\ of the testicular mitoses of the 

 abnormal pig shows chromosome numbers varying between 19 and 51, 

 Avith an "average" of 49. It was assumed that the probable number of 

 49 was correct.'*^ This should result from the fecundation of a diploid 

 egg w:ith 2 X 15 chromosomes by a spermatozoon with 19 chromo- 

 somes. EA-idence for this is given from the chromosome count of a 

 normal l^rother of this pig. Avhich had 34 (19+15) chromosomes. 

 HoAveAcr, one of the authors mentions as an interesting point that 

 ancuploid cells could be ol>scrved in the so-called triploid.^'* 



From these descriptions it is apparent. (1) that colchicine may 

 have altered the second meiotic division of the egg, but that only in- 

 direct evidence is produced, and that the concentration present Avhen 

 the sperm reached the eggs is unknoAvn: (2) that no polyploid ani- 

 mals have been produced by colchicine, Avhile other methods have 

 proved quite efficient in amphibia; (3) that triploidy is not proven, 

 and that aneuploidy is possible. 



It remains possible that colchicine may prove as useful in poly- 

 ploidy breeding in animals as in plants, but the premature claims of 

 the Swedish authors do not rest on firm ground. The technique of 

 insemination Avith colchicine is open to criticism, and even more, the 



