452 Haploids and Autopolyploids 



that fewer cells develop and the size of the organs and of the 

 body is the same as in diploids. The cause of this regulation 

 is not understood, but in general amphibian embryos appear to 

 have considerable regulatory power, as the result of which nor- 

 mal or nearly normal embryos are produced in spite of serious 

 disturbances. 



Higher Autopolyploids 



Autopolyploids with more than four complete sets of chromo- 

 somes are known but are far less common than autotetraploids. 

 Meiosis is generally more irregular in these forms, and there are 



A4 



Fig. 130. Chromosomes in the metaphase of the root tips of diploid 

 (left) and pentaploid plants of Crepis. Homologous chromosomes are 

 indicated by the same letter. The chromosomes in these forms can be 

 identified by their morphology. (Redrawn from Navashin in Genetics.) 



often configurations of more than five chromosomes. One ap- 

 parently clear case of pentaploidy was reported by Navashin in 

 a species of Crepis. A genome of this species consists of three 

 chromosomes. Chromosome A is long, with a very long and a 

 relatively short arm. Chromosome C has a long and a very 

 short arm. Chromosome D is readily identified by a satellite. 

 These chromosomes are readily identified in somatic cells of the 

 pentaploid, where it is observed that there are five of each 

 (Fig. 130). Miintzing has described meiotic behavior in penta- 

 ploids of the orchard grass, and they seen^ to be typical. 

 Meiosis is characterized by a variable number of configurations 



