THE INFLUENCE OF SOME AMINO-ACIDS ON THE 

 DEVELOPMENT OF ECHINODERMS. 1 



A. P. MATHEWS. 



While a great deal has been done on the influence of various 

 external factors on development, little is known concerning the 

 influence of those various metabolic products produced by the 

 organism itself. It is probable that such products influence both 

 the rate and character of development and it has long seemed to 

 me that by varying them we could most surely reach our goal of 

 an understanding and control of the mechanism of development. 

 Accordingly I added to sea-water containing developing eggs of 

 the sea-urchin, Arbacia pnnctulata, various amounts of cystin, 

 leucin and tyrosin to see what changes would be produced in 

 development. 



The most interesting result was obtained with cystin. Cystin 

 is the sulfur-containing amino-acid of the albumin molecule and 

 has the composition, C 6 S 2 N 2 H 12 O 4 . The sample I used was ob- 

 tained by Morner's method from horn. It is almost insoluble in 

 cold water. One hundred cubic centimeters of sea-water were 

 shaken for a moment with about a centigram of crystalline cystin 

 and the mixture poured into a finger bowl with the undissolved 

 cystin. The eggs, fertilized something less than an hour before, 

 the time varying in different experiments, were then added and the 

 eggs lay during development among the crystals of cystin at the 

 bottom of the dish. At the same time similar transfers from the 

 same lot of eggs were made to sea- water shaken in the same way 

 but without the cystin. This was to throw out the possibility 

 that aeration or some other factor was responsible for the results 

 obtained. 



The sea-urchin eggs this summer showed again, in many in- 

 stances, the remarkable peculiarity recorded by Whitcher 2 and 

 myself, a large number of eggs while living for several days not 

 forming plutei, or but a small per cent, of irregular plutei, and 

 the proportion of these going abnormally was increased by the 



1 From the Marine Biological Laboratory, Woods Holl. 



2 Mathews and Whitcher, Amer. Journal of Physiol., VIII., 1903, p. 300. 



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