430 GRACE MEDES 



SOJMABY 



In eonclusioii. the experinieaits recorded above tend to show 

 that: 



1. The factor? producing variations in the growth and de- 

 vdopment of the larvae of Arbacia puncttilata are of two t j'pes, — 

 non-«ivii\>mneQtal or intrinsic and aiviionmental or extrinsic. 



2. Among the factors of a non-environmental nature are. — 



a. Diffaent reaction of the offspring of the same parents to 

 jdrmfbir environmetttal conditions. 



b. Differeait reaction of the offspring of different parents to 

 identical eriviTonm)»ital conditions. 



c. Different reaction of eg^ pretduced at different seasons to 

 sjmilar environmental conditions. 



d- Staleness of the sexual products. 



3- Among the factors of an emviionmental nature are. — 



a. Modifications in the conc«itra,tion of the sea-water. 



b. Modifications in the alkalinity of the sea-water. 



c. Modifications in the 3alt-cont«it of the sea- water. 



d. Accunralations of the products of metabolism in the sur- 

 rounding mediunL 



4. Each modification of an «ivironm«ital nature produces its 

 ^)ecific effect upon growth. 



If two or more factors in the medium are varied, in case the 

 noodifications are of an antagonistic nature, the effects of one 

 may eomplet^y mask the eSects of the other; in case both fac- 

 tors tend to produce the same result, the combined effect may 

 be greater than that of ether one alone. 



du Sudden change of medium produces an inhibition of growth. 



If the change be gradual, and from one of less to one of more 

 favorable medium, a complete compensation for eariy iohibi- 

 tion may occur, but the ultimate growth is not equal to that 

 which would have occurred had the lan-ae been subjected during 

 the entire period to the more favorable environment. 



If the transfo' be gradual and to a less favorable medium, the 

 injury would not be so great as if the larvae had been subjected 

 eontinuou^ to the adveise conditions. 



6. Size and degree of devdopment are not correlated. 



Increased size is not coirdated with increased vigor. 



