In a review of Mr. Dendy’s work on the Homocœla, I briefly described (p. 628) the “flask-shaped” or “glandular” epithelium, which I believe to form the most common external covering in all groups of sponges. On p. 631 are shortly mentioned certain other granular cells, believed by Metschnikoff to be mesodermal, and by Dendy to be the dwelling place of symbiotic Algae; I proposed the neutral name of “Metschnikoff cells.”