94 



LEONARD W. WILLIAMS 



EXPLANATION OF FIGURES 



All fifiiuros arc from series in the Harvard Ein})r3-ological Collection. All figures 

 except the text figure, are of tlie same magnification, 280 diameters. 



Figures 1 to 9 represent transverse sections through the middle of one somite 

 of the second segment of chick embryos. 



1 From an embryo of two segments. Series 627, section 107. 



2 From an embryo of three segments. Series 629, section 100. 



3 From an embryo of six segments. Series 632, section 120. 



4 From an embryo of nine segments. Series 645, section 149. 



5 From an embryo of twelve segments. Series 1449, section 183. 



6 From an embryo of fifteen segments. Series 1460, section 103. 



7 From an embryo of eighteen segments. Series 1466, section 170. 



8 From an embryo of twenty-five segments. Series 89, section 144. 



9 From an embryo of forty segments. Series 100, section 150. 



Figures 10 to 15 represent similar sections through one of the somites of the last 

 segment of embryos of different ages. 



10 From an embryo of five segments. Series 632, section 141. 



11 From an embryo of ten segments. Series 42, section 257. 



12 F'rom an embryo of fifteen segments. Series 1460, section 314. 



13 From an embryo of twenty-five segments. Series 89, section 408. 



14 From an embryo of thirty segments. Series 95, section 395. 



15 From an embryo of forty-four segments. Series 98, section 287. 



16 Somewhat oblique transverse section of one dermomyotome of the twenty- 

 sixth segment of an embryo of forty-four segments. Series 98, section 257. 



17 Frontal section through the left somite of the tenth segment of an embryo 

 of forty segments. Series 100, section 50. 



18 Transverse section of one dermomyotome of the forty-fourth segment of an 

 embryo of fifty-two segments (5 days, 16 hours). Series 344, section 228. 



