46 A. P. MATHEWS. 



ultimately killed. With weaker solutions the results were uncer- 

 tain. In some cases the development was slightly accelerated, 

 but more often it was either not affected or else retarded. 



Impure leucin prepared from horn proved very toxic, possibly 

 owing to some impurity, but possibly to the leucin itself. The 

 effect of a weak solution is extremely interesting in that it arrested 

 development without killing the eggs. Particularly it prevented 

 development beyond the blastula stage. The embryos were 

 unable to escape from the membranes ; they remained without 

 farther development in these membranes but still alive, for 24 to 

 72 hours. The color gradually disappeared until they were as 

 colorless as star-fish larvae. I took some of them out to fresh 

 sea-water after being thus blastulae for 30 to 40 hours, to see 

 whether their subsequent development would be interfered with. 

 After a time the embryos emerged from the membranes and 

 swam about ; they lived for days and developed into all sorts of 

 fantastic embryos. Some of them were totally unlike Arbacia 

 larvae. In many, evagination of the entoderm instead of invagi- 

 nation, took place. A few developed a ciliated band in the shape 

 of the star-fish bipinnaria larvae which they resembled far more 

 nearly than they did Arbacia. These forms, however, never 

 developed a well marked entoderm like that of the star-fish, nor 

 did the mouth and anus invaginate. Another highly interesting 

 form was perfectly spherical with a single ciliated band about the 

 middle and swimming rapidly. It looked in its external form like 

 a very small trochophore. Obviously the sample of leucin which 

 was used checked some particular development but allowed other 

 processes to go on so that the embryos lived but developed in a 

 widely different direction from normal. I know of no means of 

 proving so clearly the infinite number of different embryonic forms 

 resident in each egg. Possibly an examination of these differ- 

 ent forms might be of decided interest, and I hope that some 

 embryologist may think the subject worth investigating since 

 it lies apart from my own field. I was unable to make all the 

 embryos abnormal in one direction by leucin, but I did not 

 particularly investigate this possibility. 



These experiments show that the products of intracellular 

 protein digestion may be very important in determining develop- 

 ment. 



