442 MORGAN. [Vol. X. 



1 . The embryo can elongate posteriorly without the addition 

 of material from the germ-ring. 



2. Under normal conditions a certain amount of material 

 passes from the germ-ring into the embryo. 



Another interpretation of the results of such an experiment 

 suggested itself early in the work. If one-half of the early 

 two-cell stage may develop a perfect embryo, why may not the 

 embryo cut off from the germ-ring also reproduce the rest of 

 the body on the injured side .-* An answer was not far to seek. 

 The early stages of development are passed through quite 

 rapidly, and if one-half of the embryo were regenerating it 

 would certainly lag behind the normal half, and the embryo 

 would bend over towards the regenerating side. But a study 

 of the embryo shows that there is very little, if any, delay in 

 the elongation of the embryo. The tail-knob and neuro-noto- 

 chordal plate elongate symmetrically, and only the mesoderm 

 is unsymmetrically developed. These facts, taken in connection 

 with a study of the normal processes, exclude any interpreta- 

 tion of the phenomenon as involving regeneration. 



Abnormal Development. 



Attempts were made to modify the development of the em- 

 bryo, by placing the developing eggs of Ctenolabrus into artifi- 

 cial media. The addition of more salt to the sea-water (i to 5 

 parts to 100 parts sea-water) gave no results of interest. 

 Many embryos developed normally in the more dilute solution 

 (i part NaCl), but nearly all died in the more concentrated 

 solution (5 parts). The eggs had been put into the solutions 

 when the embryo had just appeared. Another lot were placed 

 in the solution when the embryo had reached the equator of 

 the eggs, but the same results followed. 



The addition of alcohol to the extent of i /o to the sea- water, 

 did not seem to seriously affect the development of the em- 

 bryos. The addition of 2^/2.^0 of alcohol delayed the closure 

 of the blastopore in many of the eggs, and killed some 

 outright. Stronger solutions of alcohol {5/0 and lofo) killed 

 the embryos very quickly. 



