EXPLANATION OF PLATES Vf, VII, VIII, AND IX. 



F. To show the latest stage of the rudimentary nephridium of the first somite 

 (*. 0. 1), in close contact with the outer side of the hind part of the brain (a 

 few nuclei of the latter are indicated). Zeiss's D, oc. 2. Reduced |. 



Fig. 51. — One side of a transverse section through the brain of a late em- 

 bryo of Stage F. To show the two separate parts of tbe first somite. The 

 cerebral grooves are closed. Reduced |. 



Fig. 52. — Transverse section of the sixth leg of an old embryo of Stage f. 

 To show the funnel-shaped opening (/.) of the tubular portion of the nephridium 

 into the vesicular internal portion {L s. ?;.), and the relation ol' the latter to the 

 body cavity (pseudoeoele) of the leg {(>. app.). Zeiss's D, oc. 2. Reduced \. 



Fig. 53, a and b. Longitudinal horizontal sections of two contiguous legs 

 of an embryo of same stage as last. Reduced \. 



