166 



EDWIN G. CONKLIN 



in large organs where it is impossible to be certain that precisely 

 corresponding cells have been measured, that no great reliance 

 can be placed upon such measurements and comparisons; this is 

 the case with the epithelium of the mantle, stomach and kidney. 

 On the other hand in organs which consist of relatively few cells, 

 or where the individual cells are easily identified, much confi- 

 dence can be placed in these measurements; this is the case with 

 the cells of the gill filaments, osphradium, liver ducts, muscles, 

 and sex cells. 



TABLE 2 

 Size of adult tissue cells in different species of Crepidula 



