146 



O. C. GLASKK. 



in Fasciolaria, and are remarkable not for their size and posi- 

 tion on the embryo, but also because they seem to take a very 

 important part in the economy of the larva. Both the presence 

 and the activity of these remarkable bodies are of interest when 

 considered in the light of the feeding habits just described, for 

 these, as might be expected, tax to the utmost the powers of 

 assimilation and excretion. 



Without considering the cytological changes which occur in the 

 kidney cells, and which have been described fully in another 

 place ('05) I will mention some of the more important alterations 

 which involve the entire organs. What Conklin ('97) has said of 

 the excretory cells of Crepidula applies equally well to those of 

 Fasciolaria : "In the early stages these cells form a part of the 



FIG. 4. Vertical section through external kidney of F,isciolnria showing connec- 

 tion with unmodified ectoderm and the plug (f>lg.) of undifferentiated cells which 



later fill the lumen. 



y obj. 8 oc. 

 Leitz " . Drawn by Mr. Larl Kellner. 



ectodermic layer, but as the embryo grows older they grow more 

 prominent, and the whole mass is constricted at the base, so that 

 it becomes pear-shaped, the narrow end being attached to the 

 embryo, and the larger end being distal. The surrounding ecto- 

 derm cells crowd in at the neck of this constriction and work 

 their way entirely beneath these excretory cells." 



In F'asciolaria three very important changes take place in addi- 

 tion to those already mentioned. The ectoderm cells which 



