ARTIFICIAL PARTHENOGENESIS 57 1 



to hold the same view. E. N. Harvey, though believing that the mem- 

 brane is not present before fertilization, considers the jelly unnecessary 

 for its formation, holding that the membrane substance hardens on con- 

 tact with sea water. He admits that unfertilized eggs from which the 

 jelly is removed soon lose their power of forming membranes on fertili- 

 zation, but says they do not lose it immediately. Perhaps he left a 

 thin film of jelly adhering to the eggs or had not removed the water 

 containing the dissolved jelly. This dissolved jelly may be in time 

 decomposed by bacteria and thus prevent membrane formation. If 

 eggs with jelly remain in sea water fifty-two hours, they do not form 

 membranes on fertilization. 



When a sea urchin's egg is fertilized, an increase in the rate of 

 respiration occurs, as shown by 0. Warburg. This may be due to some 

 physical change, and is to be expected, since the egg passes from a state 

 of inactivity to one of activity. When the starfish egg is liberated from 

 the body of the female into the sea, it becomes active to the extent of 

 extruding the polar bodies. Loeb and Wasteneys found that respiration 

 was high at the time of formation of the polar bodies in the starfish 

 egg, and continued about the same level, whether fertilized or not. The 

 egg may pass through an inactive stage while in the ovary, with cor- 

 responding low respiration. Coming in contact with sea water may 

 stimulate it toward development, with resulting maturation and in- 

 creased respiration, though the stimulus is not sufficient to cause seg- 

 mentation. This is in harmony with the fact that much weaker stimuli 

 cause segmentation in starfish than are required by sea urchin eggs. 

 The frog's egg resembles the former and Batallion has shown that the 

 slight prick of a needle is sufficient to cause the frog's egg to segment, 

 while needles have been thrust by the writer all the way through sea 

 urchin's eggs without causing either segmentation or death. 



0. Warburg has shown that the respiration of all developing eggs 

 is high, regardless of the methods used to cause segmentation. Eespi- 

 ration is therefore essential to development. Cleavage once started may 

 be slowed or stopped entirely without materially decreasing respiration, 

 indicating that respiration is not a result of cleavage. In order to dis- 

 cuss the relation of respiration to development, it is necessary to go 

 more into detail on the general question of respiration. 



Oxidation or Cell Eespieation" 



As is well known, the heat of a flame is unnecessary for the burning 

 (oxidation) of many substances. For example, coal oxidizes slowly in 

 the air, decreasing in weight, a fact which has led to efforts to preserve 

 its fuel value by keeping it under water. Naturally, even slow com- 

 bustion generates heat, and if the heat be confined, results in spon- 

 taneous combustion, i. e., the raising of the temperature to the flame 

 point. 



