488 E. A. MINOHIN. 



Since Metsclinikoff's description of these cells they do not 

 seem to have been much noticed until comparatively recent 

 times. In the eighties we can refer only to Carter, who 

 observed them in coriacea (1884, p. 20, and pp. 21, 22), and 

 described their granules as " spherical, translucent, and glairy, 

 glistening from refraction of light, of a faint yellow tinge," 

 appearing, " when in situ among the spicules and spongozoa, 

 to be loosely grouped round a delicate nucleated cell respec- 

 tively, the ' Kern ' of Haeckel.^^ This description betrays a 

 strange confusion between cell and nucleus, as well as a com- 

 plete misapprehension on the part of the author as to the 

 meaning of the word " Kern." The author gives some 

 microchemical reactions observed, and mentions that in 

 the colour varieties of the sponges they are the seat of the 

 colours ; the possibility is suggested " that they grow into 

 the larger cells of the protoplasm (the ' Kerne ') from which 

 they appear to be derived, when they may fulfil other offices." 

 It is evident that the author's description includes dermal epi- 

 thelium as well as porocytes. Dendy figured and described 

 })orocytes in " Leuco solenia " (Clathriua) cavata (1891 

 [2], pp. 18, 19, and pi. vi, figs. 4 and 5), and considered them, 

 as well as those seen by Carter, as symbiotic algae. Bidder (1891) 

 was the first to recognise their true nature as closed pores in 

 clathrus and primordialis, though I cannot follow him in 

 the account he gives of their origin as "metamorphosed collar- 

 cells/' and am doubtful about the excretory function which he 

 ascribed to them, a view which he developed further in later 

 contributions (1892, &c.). Bidder proposed for these elements 

 the technical term " Metschnikoff's cells," and pointed out 

 correctly that their granules only differed from those in the 

 cells of the dermal epithelium in being of larger size. 



In the same year Lendenfeld figured and described these 

 cells in "Ascetta" spinosa (1891, fig. 22, p. 205), and 

 apparently also in primordialis (1. c, fig. 23, pp. 201, 202) 

 and clathrus (p. 212). In the case of spinosa he inter- 

 preted these cells as " parasites or symbiontes of vegetable 

 nature," as Dendy had done before him. In the case of pri- 



