1 66 DYNAMICS OF LIVING MATTER 



means.* The publication of Tichomiroff caused Dewitz to make simi- 

 lar experiments on the eggs of frogs, and he believed that he found that 

 treatment of these eggs with corrosive sublimate caused them to seg- 

 ment.f Roux, however, showed that Dewitz's conclusion was ■ based 

 upon an error, inasmuch as the eggs did not segment, but underwent 

 coagulation, which gave the surface of the egg occasionally the appear- 

 ance of having segmented. 



A Russian author, Kulagin, made the statement that he put fish eggs 

 into diphtheria antitoxine and saw a segmentation ; but inasmuch as he 

 published but this one statement on the subject, it is hard to tell whether 

 or not sources of error were sufficiently avoided. 



In 1887, O. and R. Hertwig published their well-known experiments 

 on the effects of various poisons on the segmentation of the eggs of Echino- 

 derms. During these experiments, R. Hertwig made the observation 

 that if eggs are transitorily treated with a o.i per cent solution of sul- 

 phate of strychnia, and are then put back into sea water, these eggs 

 show karyokinetic figures, and occasionally segment. This observa- 

 tion was repeatedly discussed by him in subsequent papers.J Hertwig 

 raised the question whether other media might not have similar effects. 

 Mead§ found in Woods Hole, that if a little KCl is added to sea water, 

 the eggs of ChcBtoptorus, a marine Annelid, throw out their polar bodies, 

 a process which in this form is normally only produced by the entrance 

 of a spermatozoon into the egg. NaCl has no such effect. Mo^^an 

 tried the effect of the addition of NaCl and other salts to sea water on 

 unfertilized eggs of sea urchins, in order to test some statements made 

 by myself and Norman concerning the effects of these salts on fertilized 

 eggs. He found that unfertilized eggs form artificial astrospheres in such 

 solutions, II and afterwardlT made the important observation that if these 

 eggs are put back into normal sea water, they may begin to" segment. 

 He states, however, that "the result is a mass of extremely minute 

 granules or pieces. These pieces never acquire cilia and do not produce 

 any form that resembles any stage of the normal embryo. Later the 

 masses disintegrate " (p. 454). The pathological cases of tumors, 

 or galls show also that cell division and growth may be produced, 

 which do not lead to the formation of an embryo. 



I was led to try experiments on artificial parthenogenesis in order 



* M. Nussbaum, Archiv fiir mikrosk. AnaU, Vol. 53, p. 444, 1899. 



t J. Dewitz, Biol. Centralblatt, Vol. 7, p. 93, 1887. 



% R. Hertwig, Ueber Befruchtung und Conjugation, V'erhandl. der detttsch. zoolog. 

 GeseUsch., 1892 ; and Sitzungsber. der Geselhch. fiir Morphologic und Physiologic, in 

 Miinchen, 1895 ! ^"'l Festschrift fiir Gegenbauer, Vol, 2, p. 23, 1896. 



§ A. D. Mead, Lectures Delivered at Woods Hole, Boston, 1898. 



II T. H. Morgan, Archiv fiir Entwickelungsmcchanik, Vol. 3, p. 339, 1896. 

 \ T. H. Morgan, Archiv fiir Entwickelungsmcchanik, Vol. 8, p. 448, 1899. 



