Note 28 — Chapter V · THE MORPHOLOGICAL COMPOSITION OF ANIMALS, CONTINUED.

Prof. MacBride corrects this statement by saying that “The ctenidia or gills (which in Mollusca generally are represented only by a single pair) are here represented by a large number of pairs; they do not, however, correspond in either number or position to the shell plates.” It may, I think, be contended that if these had any morphological significance, they would not differ in arrangement from the shell plates, and would not be limited to this special type of Mollusc.