426 J. F. MeClendon. 
reorganized under the influence of the half embryo into the miss- 
ing half. The occurrence of post-generation, and especially the 
third type, has been denied by a number of investigators who 
repeated this experiment. Laquer* has reinvestigated the ques- 
tion. 
This production of a half embryo from one blastomere is not 
due to the inability of the egg to produce more than one embryo, 
since Schultze produced double forms by inverting the egg in the 
two-cell stage, and Morgan® produced a complete embryo from 
one blastomere by pricking the other blastomere and then invert- 
ing the egg. In order to determine whether this inversion of the 
egg and consequent stirring up of its contents is necessary for the 
production of a complete embryo from one blastomere, I attempt- 
ed to find a frog’s egg that would permit the complete removal of 
one blastomere without death of the egg. No one has hitherto 
been able to do this, although Roux® observed a partial but very 
abnormal development of extra-ovates of the frog’s egg. 
Last spring at Columbia, Missouri, I located the breeding 
places of Rana pipiens and Chorophilus triseriatus. The unseg- 
mented eggs of both species could be collected in the ponds and 
small streams, or in the frog cages in the laboratory, the eggs of 
the latter species being more easily obtained. 
I tried various methods of removing one blastomere in the two- 
cell stage. It was possible to suck out one blastomere with a 
capillary pipette connected with a rubber tube, one end of which 
was held in the mouth, but it was very difficult to pierce the jelly 
with the pipette without killing the egg, and the suction often 
removed both blastomeres. A better way of making a hole in the 
jelly was the time honored method of piercing it with a hot 
needle. A very coarse needle was used and heated to a tempera- 
ture that would coagulate a portion of the blastomere into which 
it was thrust. On withdrawing the needle, the coagulated parts of 
the jelly and blastomere were pulled out, thus leaving a large hole 
“Arch. f. Entwicklungs. 1909, XXVIII, p. 327. 
‘Arch. f. Entwicklungsmech., I. p. 298. 
*Anat. Anz., 1895, X. p. 5238. 
*Jahresbericht d. Schles. Ges. f. vaterl. Cultur, Juni, 1887. 
