262 KINGS LEY. 



EXPLANATION OF PLATE X. 



Fig. 40. Longitudinal section of an embryo with cephalic and caudal areas 

 and one intermediate somite developed. The arrows mark the limits of the 

 somite. 



Fig. 41. Through primitive streak in advance of mouth, Stage C, early. 



Fig. 42. Transverse through the posterior primitive streak, Stage C, early. 



Fig. 43. Transverse through the anterior end of the primitive streak 

 ("mouth"), showing coelom of somite I, Stage C, early. 



Fig. 44. Through primitive streak and marginal groove. Stage C, early. 



Fig. 45. Longitudinal section through an embryo of Stage C, late. 



Fig. 46. Longitudinal section (a little oblique) through an embryo, with eight 

 somites developed, showing a coelomic cavity developed in each of the anterior 

 seven somites. 



Fig. 47. Obliquely transverse section. Stage C, showing the neural anlage, 

 ccelom I, and the segmental structure (? gland) of somite II. 



Fig. 48. Through somite V, Stage C, late. (Through a misunderstanding on 

 the part of the lithographer this and Figs. 49 and 52, representing only one side 

 of the body, are so turned upon the plate that the median plane is oblique.) 



Fig. 49. Transverse through the abdomen. Stage C, late. 



Fig. 50. Transverse through somite IV, showing the segmental structure 

 (dorsal organ) of that somite, Stage D. 



Figs. 51, 52, 53. Transverse sections through somites V, VI, and VII, Stage 

 E, showing the ccelomic cavities in each and the segmental structures (.'' glands) 

 in V and VI. 



Fig. 54 a-i. Modifications of the coelom of somite V, Stage H, into the ne- 

 phridium ; Fig. 54 i is the most anterior. In this «. a. refers to the anterior bend 

 of the nephridial tube. 



Fig. 55, Reconstruction (by plotting) of the nephridium of Fig. 54. 



