November 21, 1913] 



SCIENCE 



749 



sufficiently large to insure a permanent value 

 to this collection, and to warrant an attempt 

 to make it as complete and comprehensive as 

 may be practicable. 



Frederick V. Coville, 

 Curator of Botany 



SPECIAL ABTICLES 



REVERSIBILITY IN ARTIFICIAL PARTHENOGENESIS 

 I 



In 1900 the writer pointed out that in 

 Campanularia a highly differentiated organ 

 like the polyp may be transformed into the less 

 differentiated material of the stem, which in 

 turn may form a new polyp.-' Since then, rever- 

 sibility of certain phenomena of differentiation 

 has been observed by Driesch, Child, F. Lillie, 

 Schultz and others. 



The writer has repeatedly tried to reverse 

 the phenomena of development in the egg of 

 Strong ylocentrotus fertilized with sperm but 

 thus far without success. Experiments on 

 artificial parthenogenesis, however, gave posi- 

 tive results. 



It is difficult to cause artificial partheno- 

 genesis in the eggs of the Californian sea 

 urchin with hypertonic sea water. If we treat 

 these eggs for about 2 or 2^ hours with such a 

 solution (50 c.c. sea water + 8 c.c. 2i m NaCl 

 +■ CaCl, -[- KCl) it often happens that a cer- 

 tain percentage of eggs, after they have been 

 returned to normal sea water, begin to seg- 

 ment regularly in 2, 4 or even 8 or 16 cells. 

 They then stop developing and go into the 

 condition resembling that of a resting egg. If 

 such blastomeres are at any time fertilized 

 with sperm they will develop into larvae in a 

 perfectly normal way.- These observations 

 show incidentally that it is not the lack of the 

 organs of cell division which prevents the un- 

 fertilized eggs from developing, since these 

 eggs had been in possession of these organs. 



The writer has shown that the induction of 

 development in the egg is due to a combina- 

 tion of at least two agencies. The one causes 



1 Am. Jour. Physiol., IV., 60, 1900. 



2 Arch. f. EntwicMgsmech., XXIII., 479, 1907; 

 Jour. Exper. Zool, XV., 201, 1913. 



an alteration of the surface (which may or 

 may not be followed by a membrane forma- 

 tion) and this alteration starts the develop- 

 ment of the egg, but leaves it, in many cases 

 at least, in a sickly condition from which it 

 can be freed by the application of the second, 

 corrective agency. The alteration of the sur- 

 face may be caused by any of those substances 

 or conditions which cause hemolysis: acids, 

 bases, hydrocarbons, hypertonic and hypo- 

 tonic salt solutions, foreign blood, etc. The 

 second, curative effect may be produced by a 

 short treatment of the egg with a hypertonic 

 solution or by a suppression of the develop- 

 ment of the egg for a somewhat longer period 

 by lack of oxygen or by KCN. One method 

 of causing artificial parthenogenesis in the 

 eggs of Ariacia consists in putting them for 

 about 20 minutes into a mixture of 50 c.c. 

 m/2 (NaCl + KCl + CaCI.) + 0.3 c.c. N/10 

 NHjOH and subsequently into a neutral 

 hjrpertonic solution for from 15 to 20 minutes 

 (the figures are given for about 22° C). A 

 varying percentage of eggs treated this way 

 will develop into embryos and the rest will 

 perish very rapidly. If the eggs are treated 

 with the alkaline solution alone without sub- 

 sequent treatment with the hypertonic solu- 

 tion they will begin to segment, but they will 

 perish rapidly. The alkaline treatment alone 

 induces the change in the surface of the egg 

 required to start the development, but this, 

 without the corrective treatment, leads only 

 to the first segmentations followed by a rapid 

 disintegration. 



The writer found last summer that these 

 effects are reversible in the eggs of Arhacia. 

 If, after the treatment with alkaline solution 

 alone or with alkaline and hypertonic solution, 

 the eggs of Arhacia are put for a sufficient 

 length of time into sea water containing a 

 certain amount of NaCN or of chloralhydrate, 

 they go back into the resting stage and behave 

 in appearance and reaction like unfertilized 

 eggs. Both the NaCN and the chloralhydrate 

 prevent the developmental processes in the 

 egg. The suppression of these processes of 

 development reverses the changes induced in 

 the egg by the treatment with alkali. If after 



