INITIATION OF DEVELOPMENT IN CH/ETOPTERUS. 59 



of magnesium chloride, calcium chloride, cane sugar, potassium 

 bromide, potassium nitrate and potassium sulphate. Tin- egg 

 must be in a very labile state, such that almost any slight impetus 

 will force it from its condition of unstable equilibrium. 



There are, however, indications of specific needs of the egg, 

 satisfied more or less completely by the various methods of 

 treatment. One of the most obvious needs, it seems to me, is for 

 oxygen. In this respect, as before stated, there shows up a 

 distinct difference between the maturation and differentiation 

 processes. Although maturation is called out in lack of oxygen 

 or in low rate of oxidation, differentiation, at least to the point of 

 forming swimmers, is often interfered with by these conditions. 

 A brief suppression of oxidation by potassium cyanide, following 

 potassium chloride interfered with the production of swimmers 

 in CJmtopterus. On the other hand, increased supply of oxygen 

 in the sea-water after treatment with potassium chloride led 

 to some of the best results obtained. By far the most normal 

 results were obtained from the application of heat for a stated 

 length of time. Although heat may act in many ways, it is very 

 probable that one of its effects is to increase the rate of oxidations 

 within the egg. It is also well-known that heat increases the 

 permeability of certain membranes to oxygen. It may be, there- 

 fore, that heat is an important aid to the oxidations necessary to 

 differentiation. Greater oxygen pressure in the sea-w r ater sur- 

 rounding the egg will supply the need to a certain extent, but 

 not so surely as will heat. 



In plant seeds it has been found by Crocker ('06) in several 

 cases, that the factor which causes the dormant period between 

 the formation of the embryo and the germination of the seed is 

 an insufficiency of oxygen in the seed due to the semi-perrneability 

 of a membrane of the seed to oxygen. When greater oxygen 

 pressure was supplied the delayed germination proceeded. In 

 one case heat increased the permeability of the membrane to 

 oxygen and brought about the same result as did increased 

 oxygen pressure in the environment of the seed. The seed in its 

 dormant condition is of course different from the unfertilized 

 egg in that the embryo is already formed, but the conditions 

 that determine dormancy and the awakening from dormancy may 



