The Role of Nucleus and Cytoplasm 



133 



poorly formed, the circulation was blocked 

 at various points, and the gut retained its 

 main mass of yolk. All became edematous 

 and ascitic and died withovit feeding within 

 twelve to eighteen days from fertilization. 

 The majority of the haploids from small eggs 

 showed a more nearly normal circulation and 



loid newt larvae developed from whole eggs. 

 Various hypotheses have been proposed to 

 account for the poor viability of experimen- 

 tally produced haploids (see the reviews in 

 Fankhauser, '37, '45a). One of the most 

 tempting is the suggestion that lethal or at 

 least viability-reducing genes may be pres- 



Triturus viridescens 



T. pyrrhogaster 



T. taeniatus 

 T. palmatus 

 T. alpestris 



T. cristatus 

 T. granulosus 



Eurycea bislineata 



Rana esculenta 

 R. temporaria 



R. pipiens 



R. nigromaculata 



Triploid 



Tetraploid 



Pentaploid 



Triploid 



Pentaploid 



Triploid 



Pentaploid 



Pleurodeles waltlii 



Amblystoma mexicamun Triploid 

 (axolotl) Tetraploid 



Pentaploid 



Triploid 

 Tetraploid 

 Triploid 

 Triploid 



Triploid (cold) 

 Triploid (heat) 



Triploid (cold) 

 Triploid (heat) 



Tetraploid (cold) 

 Triploid (cold) 

 Triploid (cold) 

 Triploid (cold) 

 Tetraploid (cold) 

 Triploid (cold) 

 Triploid (cold) 

 Tetraploid (cold) 

 Triploid 

 Triploid (cold) 

 Tetraploid* 

 Pentaploid* 

 Hexaploid* 

 Heptaploid* 



Triploid, tetraploid, pentaploid 

 (colchicine, sulfanilamide) 



Triploid (heat) 



Triploid (parthenogenesis) 



Triploid (cold) 



Triploid 1 among partheno- 

 Tetraploid > genetic larvae 

 Hexaploid J 



Fankhauser, '38b, '45a; 

 Fankhauser and Griffiths, '39; 

 Fankhauser and Watson, '42 

 Kawamura, '41a; 

 Fankhauser, Crotta and Perrot, 



'42; 

 Sanada, '51 

 Book, '41, '45 

 Fischberg, '47 b 

 Fischberg, '44, '47a 



Fischberg, '47b 

 Costello, '42; 



Costello and Holmquist, unpub. 

 Gallien and Muguard, '50 

 Fankhauser and Humphrey, '42, 

 '50, and unpublished 



Fankhauser, '39 



G. and P. Hertwig, 

 Jahn, '52 



Briggs, '47 

 Parmenter, '33 

 Kawamura, '41b 



Kawamura, '39 



'20 



* Among offspring of triploid females mated with diploid males. 



a normal utilization of the yolk supply in 

 the gvit. Two-thirds of the total were able 

 to feed and did not show edema or ascites; 

 they survived for periods up to nine months, 

 without luidergoing metamorphosis. The re- 

 duction of the initial amount of yolk may 

 have facilitated the differentiation of the 

 gut in a purely mechanical way, and, at 

 the same time, in the presence of a relatively 

 normal circulation, created the conditions 

 necessary for a more rapid and complete 

 utilization of the yolk material. 



That this yolk factor is not alone respon- 

 sible for the poor development of haploid 

 embryos in general is shown by the fre- 

 quently normal gut differentiation in hap- 



ent in most of the haploid chromosome sets 

 and exert their effect at various early stages 

 of development, unchecked by the normal 

 dominant alleles visually contained in the 

 second set of chromosomes in a diploid. The 

 existence of a recessive lethal factor which 

 kills one-quarter of the offspring of hetero- 

 zygovis parents has recently been demon- 

 strated in the axolotl (Humphrey, '48). It is 

 of the greatest interest that this factor causes 

 a fluid imbalance which appears very early 

 in development, and causes a marked en- 

 largement of the head and suprabranchial 

 region, which may extend later on to the 

 body. The effect is readily distinguishable 

 from the edema of the usual haploid syn- 



