Nucleus of the Animal and Vegetable '* Gell^ 223 



said, as well as that which is implied by what I had previous- 

 ly written, on an attractive force or suctorial power as exer- 

 cised by that nucleus ; for assuredly no other than what had 

 been such a nucleus is to be recognised in Weber's figure. 



Professor Goodsir finds his " germinal membrane," met 

 with on the free surfaces of parts or organs, to consist of 

 " cells, with their cavities flattened, so that their walls form 

 the membrane by cohering at their edges."* 



I am happy to have it in my power to confirm this obser- 

 vation, by stating that the description now quoted fully ap- 

 plies to two membranes in the mammiferous ovum seen by 

 myself, and figured in the Philosophical Transactions for 

 1839. t One of these, my " amnion," corresponds to what 

 had long been called the " germinal membrane" in the ovum 

 of the Bird : and the other I stated to be the foundation of 

 the lamina subsequently vascular. Several figures of the lat- 

 ter I have'copied on this occasion, — Plate I., figs. 33, 34 ; and 

 I recommend an attentive perusal of the description of these 

 figures. Tubes such as those entering into the formation of 

 muscle, fig. 26, and the lens, fig. 27, are certainly germinal 

 membranes ; appearing thus to have the power of absorbing 

 for nutrition. And if fig. 38 in Plate I. be referred to, it will 

 be found that the membrane of my ovisac presents a struc- 

 ture of the same kind ; which is interesting, 1. from the sub- 

 sequent ramification of numerous capillaries on it, by which 

 there is formed a Graafian vesicle, J and, 2. from its inner sur- 

 face being the situation of the " membrana granulosa," a sort 

 of epithelium. I long since shewed the incipient chorion to 

 have a like structure (Plate II., fig. 54, %) ; and, as already 

 said, there is good reason for believing it to be the struc- 

 ture of other membranes.§ 



* Loc. cit., p. 3, t Plates VII. and VIII. 



X Of which the ovisac is now the inner membrane. Phil. Trans., 1838, p. 311. 



§ While these pages are passing through the press, I learn that Professor 

 llarting of Utrecht, and ^M. Mulder, have lately found the primitive membrane 

 of the vegetable cell, even when young and before its thickening, to present 

 many povcs. This seems to be in perfect keeping with what! long since shewed 

 to be the mode of origin and structure of the membrane of the ovisac, already 



