FERTILIZATION 1 7 1 



no more able to state the nature of the forces which underlie secretion 

 in this than in any other case. 



These experiments show that it is possible to completely imitate by 

 physicochemical means the effect of the spermatozoon upon the sea^ 

 urchin egg. It is also obvious that this method is somewhat comphcated 

 and specific, and that it cannot be well covered by the phrase that the 

 method consists in a "stimulation," for the word "stimulation " does not 

 — as far as I know — mean that we have to treat an organ first for one 



half minute with 50 c.c. of sea water +3 c.c. — butyric acid and then 



for from twenty-five to fifty minutes with a mixture of 100 c.c. of sea 

 water + 14 c.c. 2^ n NaCl solution. Moreover, these quantitative data 

 Vary slightly for different species of sea urchins, e.g. Strongylocentrotus 

 purpuratus and jranciscanus. 



Yet some authors have maintained that any kind of stimulus, or 

 various chemical substances, might produce artificial parthenogenesis in 

 the egg of the sea urchin. These statements are based partly on mis- 

 understandings and partly on errors. In a former paper I stated that 

 it makes no difference how the osmotic pressure of the sea water is 

 raised, whether by sugar, by urea, or by salts; if the pressure is only 

 sufficiently high, the parthenogenetic development of the sea urchin's 

 egg will occur. Morgan makes use of this fact to attempt to show that 

 inasmuch as sugar as well as salts cause the development, various stimuli 

 can produce the development. He overlooks the fact that in this case 

 the sugar or salt does not act chemically, but solely osmotically by with- 

 drawing water from the egg, and that for this effect it is immaterial 

 what the chemical character of the dissolved substance is. Other 

 authors have been misled by mistaking parasitic larvas found in their 

 cultures for the larvte of sea urchins. Ariola has maintained that the 

 eggs of sea urchins develop normally parthenogenpticalLy at Naples. I 

 may state that neither the unfertilized eggs of Arbacia nor those of 

 Strongylocentrotus of the Atlantic or the Pacific coast of America ever 

 develop, and that the same has been found for the eggs of the sea urchins 

 at Naples by all competent workers. Ariola has given a description 

 and drawings of the larvce he found which he considered as normally 

 parthenogenetic larvae of sea urchins, and I believe that they were prob- 

 ably larvae of some mollusk; they were certainly not the larvae of the 

 sea urchin. I mention this fact simply to show that unless an author 

 actually observes the origin of a larva from the egg, he may fall into 

 serious error. Viguier maintains that the sea urchins in Algiers are 

 naturally parthenogenetic. I should place more confidence in this 

 author's statements were they written in a more dispassionate, scien- 



