52 FRANK R. LILLIE. 



On the right side there are nineteen myotomes, and on the left 

 twenty and a half. Fig. 10 shows the myotomes of the right 

 side as they appeared in an entire mount of the stained embryo 

 in oil; only 16 can be counted. But sections show, that the 

 large anterior one is really three, and the nineteenth is repre- 

 sented by the mesoblast behind the last complete somite. If we 

 reckon the three anterior somites as cephalic, this leaves sixteen 

 trunk myotomes, and the enumeration agrees with that of the 

 nerves. On the other side of the embryo there is distinctly one 

 more cephalic myotome than on the right side ; if, then, we 

 reckon four as the number of cephalic myotomes on this side/ 

 there are sixteen and a half trunk myotomes, a result that agrees 

 with the enumeration of the nerves. 



The organs in this embryo, as in the others described, have 

 developed normally as far as the cut surface. The Wolffian ducts 

 are enlarged by internal pressure. There has been no compensa- 

 tory growth and no regeneration, if we except the notochord. 



GENERAL DISCUSSION. 



The chief value of these experiments consists in the fact that 

 they clear the ground for farther researches of a more definite 

 character. It is probable that the results obtained will hold in 

 general for the Amniota, and they may, therefore, be of value in 

 the interpretation of teratological phenomena. Results that I 

 have obtained from destruction of large portions of the brain in 

 young embryos have convinced me that great caution must be 

 exercised in interpreting conditions associated with anencephaly. 

 It should be possible, and I am convinced that it is possible, to 

 produce, these various conditions experimentally. Until this is 

 done it seems to me that conclusions, based on teratological ma- 

 terial, as to the trophic value of the embryonic nervous system 

 are debatable. 



The following questions definitely raised by the experiments 

 just described may be answered here in part : 



I. As to Regeneration. The only organ showing evidence of 

 regeneration is the notochord. In all of the embryos described, 



i Froricp recognizes four cephalic myotomes in the chick ; the most anterior, how- 

 ever, becomes rudimentary at a very early stage, and soon disappears ; this condition 

 seems to have been attained on one side in this embryo, but not on the other. 



