H. E. LEHMAN 217 



cleus, although incapable of maintaining its integrity during 

 interphase and mitosis, was nevertheless able to increase in chro- 

 matin volume, presumably by utilization of nonspecific protein 

 precursors in the pipiens cytoplasm. 



The remaining studies on nuclear transplantation that have 

 been reported were carried out on eggs of the salamander, Tri- 

 turus (Triton) pahnatus (Waddington and Pantelouris, 1953; 

 Lehman, 1955). These attempts have been entirely unsuccessful 

 so far as obtaining postblastula is concerned, and no information 

 relative to progressive nuclear differentiation has been obtained 

 from these experiments. Waddington and Pantelouris injected 

 nuclei from diploid blastula, gastrula, and neurula donor cells 

 into non-nucleate halves of normally fertilized eggs. Cleavages 

 were obtained with all types of donor cells. When blastula and 

 gastrula donor cells were used, some of the cases developed into 

 abnormal arrested blastula with a reduced blastocoele filled with 

 loose cells. It was not clear from these results whether the arrest 

 in development at the blastula stage was occasioned by nuclear 

 specialization, or by operative damage, or by lack of totipotency 

 on the part of the host egg fragment. 



In view of these uncertainties, an attempt was made to repeat 

 these experiments on whole eggs of T. pahnatus ( Lehman, 1955 ) . 

 Unfortunately, Triton eggs cannot be parthenogenetically ac- 

 tivated by pricking, nor was it possible to stimulate development 

 by the injection of blastula nuclei alone. This difficulty was partly 

 circumvented by using Hugh's ( 1939 ) technique of x-iiTadiating 

 sperm at 50,000 r to inactivate the chromatin without destroying 

 the fertilizing capacity of the sperm. Although haploid embryos 

 were consistently obtained from normal eggs fertilized by such 

 sperm, the technique cannot be considered entirely satisfactory 

 since minute disorganized cliromatin fragments, probably of 

 sperm origin, were frequently observed in smear preparations. 

 These fragments, if of sperm origin, had undoubtedly undergone 

 some multiplication during development even though they were 

 not intimately associated with the division figure. The possibility 

 of some developmental effect of these degenerating "sperm 

 chromatin fragments" cannot be ignored. After fertilization with 



