The Nervous System and Salivary Glands of Phylloxera

The Nervous System and Salivary Glands of Phylloxera. I have read with interest the remarks of Dr. E. L. Mark upon this subject in PSYCHE for January. He is without doubt right in his conclusion that what I have inadvertently called nervous cords are, in reality, the tracheae ; I have been of this opinion for some time. Dr. Mark's article suggests, however, another thought which induces me to write these few lines. M. Maxime Cornu has, under the direction of the French Academy, made extended investigations into the nature of the root swellings caused by Phylloxera vastatrix, arriving at the conclusion, to me somewhat surprising, that they are purely the result of the mechanical action of the puncture made by the insect, and of the subsequent-absorption of liquids. These results are recorded in an extended and elaborately illustrated mernoir.1 I have always believed Cornu's conclusions essentially erroneous, for the following reasons, which I quote from my 6th Report on the insects of Missouri, 1873, p. 70.