264 KINGS LEY. 



EXPLANATION OF PLATE XL 



Figs. 56, 57, 58, 59 transverse sections of the nephridium, about Stage H. 

 Fig. 56, is most anterior. 



Fig. 60. Longitudinal section of the nephridium after the duct is open to the 

 exterior. The external opening is plainly on the posterior surface of the basal 

 joint of the fifth appendage while the loop of the duct extends nearly to 

 somite II L 



Fig. 61 a-e. Horizontal sections through the nephridium, Stage I. 



Fig. 61 f and g. Reconstructions (in wax) of the nephridium represented in 

 Figs 61 a-e. 



Fig. 62. Reconstruction (in wax) of the nephridium of Stage L. To be com- 

 pared with GuUand's ('85) Fig. 2. (Is exaggerated in transverse diameter.) 



Fig. 63. Longitudinal section of a portion of the abdomen showing the early 

 appearance, by splitting, of somatoplure and splanchnoplure in that region. In 

 the neural anlage («. a.) can be seen the inpushing of nuclei for rapid cell prolifera- 

 tion producing the pitted appearance shown in Fig. 29. 



Figs. 64 and 65. Transverse sections of the heart Stage H, Fig. 65, being the 

 more anterior and the plane of section 64 passing through appendage V. 



Fig. 66. Heart, transverse. Stage I. 



Fig. 67. Transverse section through abdomen, the section passing through the 

 operculum, Stage I. 



Fig. 68. From the same series as Fig. 67, but more posterior. 



Fig. 69. Transverse through oesophagus, oesophageal commissures and sternal 

 artery. Stage I. 



