224 Dr Martin Barry on the 



I had also observed and sketched, as seen both in the Fal- 

 lopian tube and at its fimbriated extremity, traces of what 

 was probably a corresponding membrane, though perhaps in 

 an incipient state (Plate II., fig. 48, 7) ; in one instance along 

 with young and blood-red epithelium cells. The latter when 

 fully formed, I had also seen and figured (Plate II., fig. 54, Q 

 " adhering by their distal extremities," in the manner de- 

 scribed by Goodsir ; as well as what appear to have been 

 cytoblasts and cells of a germinal membrane, for forming 

 epithelia, fig. 54, a, /3, 7, b. And I would offer the diagram, 

 fig. 53, in Plate II., as the probable mode of origin and evo- 

 lution of the epithelium cells. 



This diagram represents a germinal membrane, resting on 

 capillaries such as those in Jig, 48, j8, Plate II. ; having on the 

 extreme left a cytoblast, marked IV., in the state represented 

 by the woodcut, fig. 4. The cytoblast becomes a cell, 

 marked V., which is in the state of that in the woodcut, fig. 

 5. VI. In the diagram corresponds to the woodcut, fig. 6 ; 

 and so on, as far as XI.; after which the epithelium cells 

 are given off, adhering to the membrane of the cell or cells 

 in which they arose ; and leaving the nuclei, which are in out- 

 line only, in a state for producing another brood. 



This explanation, rendering it needless to suppose that 

 there occurs a splitting of the germinal m^embrane into two 

 layers, seems to meet a difficulty spoken of by Goodsir ; and 

 it probably applies as much to the supposed splitting of what 

 has been called the " germinal membrane" in the ovum ; for 

 in both there is formed a " mucous" or epithelial surface. 



But if the diagram in question explains the mode of origin 

 of epithelium cells, it may also admit of a further and a more 

 important application. I found the red colouring matter of 



mentioned in pp. 207 and 209 of this paper, and to accord with my belief in 

 the compound structure of the membrane of every cell. With regard to the 

 question at present much occuj)ying the attention of Vegetable Physiologists — 

 Whether, in the thickening of the cell-membrane, the inner or the outer layer 

 is the last formed, — all my observations on the functions of the nucleus are of 

 course in favour of the inner layer being formed last (see fig, 40.) But if the 

 primitive membrane of the cell be, as I believe, a compound structure, it has 

 in its own substance the means of contributing towards its thickening. (See 

 rhil. Trans., 1841, Tlatc XX\^, figs. 170-173.) 



