ADDRESS. 1 1 



von Baer and other observers had recognised within the animal ovum the 

 germinal vesicle, which obviously bore to the ovum the relation of a 

 nucleus to a cell. As the methods of observation improved, it was recog- 

 nised that, within the developing egg, two vesicles appeared where one 

 only had previously existed, to be followed by four vesicles, then 

 eight, and so on in multiple progression until the ovum contained a 

 multitude of vesicles, each of which possessed a nucleus. The vesicles 

 were obviously cells which had arisen within the original germ-cell or 

 ovum. These changes were systematically described by Martin Barry so 

 long ago as 1839 and 1840 in two memoirs communicated to the Royal 

 Society of London, and the appearance produced, on account of the irregu- 

 larities of the surface occasioned by the production of new vesicles, was 

 named by him the mulberry-like structure. He further pointed out that 

 the vesicles arranged themselves as a layer within the envelope of the egg 

 or zona pellucida, and that the whole embryo was composed of cells filled 

 with the foundations of other cells. He recognised that the new cells 

 were derived from the germinal vesicle or nucleus of the ovum, the con- 

 tents of which entered into the formation of the first two cells, each of 

 which had its nucleus, which in its turn resolved itself into other cells, 

 and by a repetition of the process into a greater number. The endogenous 

 origin of new cells within a pre-existing cell and the process which we 

 now term the segmentation of the yolk were successfully demonstrated. 

 In a third memoir, published in 1841, Barry definitely stated that young 

 cells originated through division of the nucleus of the parent cell, instead 

 of arising, as a product of crystallisation, in the fluid cytoblastema of the 

 parent cell or in a blastema situated external to the cell. 



In a memoir published in 1842, John Goodsir advocated the view that 

 the nucleus is the reproductive organ of the cell, and that from it, as from 

 a germinal spot, new cells were formed. In a paper, published three years 

 later, on nutritive centres, he described cells, the nuclei of which were 

 the permanent source of successive broods of young cells, which from 

 time to time occupied the cavity of the parent cell. He extended also his 

 observations on the endogenous formation of cells to the cartilage cells in 

 the process of inflammation and to other tissues undergoing pathological 

 changes. Corroborative observations on endogenous formation were also 

 given by his brother Harry Goodsir in 1845. These observations on the 

 part which the nucleus plays by cleavage in the formation of young cells 

 by endogenous development from a parent centre — that an organic con- 

 tinuity existed between a mother cell and its descendants through the 

 nucleus — constituted a great step in advance of the views entertained by 

 Schleiden and Schwann, and showed that Barry and the Goodsirs had a 

 deeper insight into the nature and functions of cells than was possessed 

 by most of their contemporaries, and are of the highest importance when 

 viewed in the light of recent observations. 



In 1841 Robert Remak published an account of the presence of two 



