Licence: Public Domain Mark
Credit: Researches in embryology. (Second series) / by Martin Barry. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![follow the same laws in their development. Thus whether a muscular fibre or a nervous tube is destined to be formed, the foundation of both consists of vesicles or cells, which have arisen in the manner above described; and it is through the modifications which the vesicles undergo, that a muscular fibre on the one hand, or a nervous tube on the other, is produced. In short, there is for all the elementary parts of organisms a common principle of development. 291. It will be interesting to refer to a few of the facts recorded in the foregoing and the previous memoir, in connexion witli the analogy now mentioned; and if those hicts should be found in any way to exemplify it, they will not be the less ad- missible from my having obsei ved them in the course of researches in which this analogy formed no part of the object I was in pursuit of. 292. Both the nucleus and nucleolus wTre figured in my First Series-f, in the peculiar granules, or rather vesicles of the ovisac, though I was ignorant of their im- portance. It will be seen indeed that those peculiar granules (vesicles) form a part of more than fifty figures in that papei, and tliat the nucleus is represented in almost every instance where tlie size admitted of it. This is mentioned merely to show that those objects (tlie nucleus and nucleolus) w^ere not overlooked, for to Schlefden belongs the merit of first pointing out the nature of those objects in plants, and to Schwann that of recognising corresponding structures in animals. That inemoir contained also the drawing of a spot;}: on the inner surface of the membrane of the yelk in the ovum of the Frog. Of that spot I did not attempt to offer any explana- tion, simply stating its appearance as a spot which I always find on the internal surface of the merabrana vitelii of the Frog in ovisacs of about this size [i']. This spot does not appear to have been hitherto described. It is genei-ally elliptic, rarely round, has a well-defined contour, and is perhaps slightly lenticular in form. In this instance it measured V-' i'^ length, and is often of about the same size. It appears to be composed of granules The spot in question is obviously the nucleus of the membrane or vesicle on the inner surface of which it occurs j|. 293. The vesicles v/hich constitute the outer portion of the mulberry-like structure (Plate VI. fig. 110., Plate VIII. fig. 130.) present each a nucleus^ and nucleolus. t L. c, Plate VIII. fig. 73. i L. c, Plate VI. fig. 28. rf', and in the present paper, Plate V. fig. 84|. § L. c, par. 40. II The existence of this spot will probably be found of some importance in determining the order of forma- tion of the several parts of which the ovum is composed. And it is proper to state, that Schleiden's discovery in plants of the origin of vesicles (cells) on a nucleus, and the extension of this discovery to animals by Schwann, must necessarily modify some of the conclusions in my First Series as to the order of formation here referred to; but in the present series this has not been the subject of investigation. I would remark, however, that if the spot on the inner surface of the membrana vitelii in the ovum of the Frog is present in the corresponding membrane of other ova, the formation of this membrane is doubtless earlier than that of the germinal vesicle itself (par. 242.). I have observed the stroma in the neighbourhood of an ovisac to appear as if composed of vesicles with nuclei. ^ It is not probable, however, that the nucleus here refeiTcd to is of the same kind as that called the Cytoblast by Schleiden (see par. 317. and its last Note.). MDCCCXXXIX. 3 A](https://iiif.wellcomecollection.org/image/b2197214x_0059.jp2/full/800%2C/0/default.jpg)
