EFFECT OF EXTRACTS UPON DEVELOPING EGGS. 95 



5. It is possible that extracts made from larvae in a certain 

 stage differ qualitatively from those made of larvae of an earlier 

 or a later stage, but we do not know that this is true, nor do we 

 know that the retardation is associated with any modification of 

 the rate of enzyme action, or permeability, or oxidation, or any 

 specific process. Probably it depends upon the great complexity 

 of the protoplasmic system, and the fact that no one part of that 

 system may be altered considerably without disturbing the equilib- 

 rium of that whole system. 



6. It is not possible to say at this point that the retardation 

 caused by the extract affects the same metabolic processes as do 

 the KCN, CH 3 COOH, NaOH, etc., but the use of the extract 

 results in arrests and retardations of development such as are 

 apt to be caused by these chemical agents, and the various types 

 of malformations resulting are often similar. 



7. This work does not indicate, then, either the presence or 

 the absence of formative stuffs, but shows that under the condi- 

 tions given they do not appear. Two possibilities present them- 

 selves. If formative stuffs exist, they would seem to be unable 

 to pass into solution in sea water, in lipoid-soluble substances, 

 and in solvents which are able to dissolve carbohydrates. There- 

 fore, if present, they appear to be complex in character and in 

 close association with the protein molecule. The other possibility 

 is that these hypothetical substances may go into solution in cer- 

 tain solvents, but yet may not be able to register any effect upon 

 the developing eggs, because the cell walls of the latter may not 

 be permeable to the formative stuffs in solution. 



1 Conklin, E. G., " Heredity and Environment," p. 185. 



2 Child and Bellamy, " Physiological Isolation by Low Temperature," Bot. 

 Gas., Vol. LXX., 1920, p. 249-267. 



3 Carnegie Institution of Washington Year Book 1918, p. 55, D. T. Mac- 

 Dougall. Report from the Department of Botanical Research, p. 55. 



4 MacBride, "Textbook of Embryology," Vol. I., p. 526-528. 



5 Driesch, 'oo, " Die isolierten Blastomeren des Echineden-Keimes Archer," 

 Ent. Mech., Vol. X. 



6 Wilson, E. B., " Experimental Studies on Germinal Localization," Journ. 

 Exp. Zoology, Vol. I., p. 197269. 



7 Conklin, E. G., " Organ-forming Substances in the Eggs of Ascidians," 

 BIOL. BULL., Vol. VIII., No. 4. 



s Morgan, T. H., " Regeneration." 



