THE CELL, OR ELEMENTARY PART. 49 



development is but a naked mass of germinal matter, with- 

 out a cell wall, but having a new centre and often numerous 

 new centres (known as germinal spots or nuclei) embedded 

 in it, enclosed in a capsule of formed material " cell wall."* 



The mode of formation of the cell, or elemental unit, 

 as well as the origin from it of other units, is well illustrated 

 in the formation of the ovum. In PI. Ill, fig 7, the cells 

 constituting the tissue of the ovary of the common stickle- 

 back are represented, and amongst them are seen true ova 

 at a very early period of development. The youngest of 

 these differs but little from the cells amongst which it lies. 

 It is, in fact, but one of these which has advanced in de- 

 velopment beyond the rest. In fig. 8, a small but complete 

 ovum is seen with its germinal, or living matter, here called 

 germinal vesicle, surrounded by the yolk which consists of 

 formed matter. In the^ germinal matter are seen numerous 

 germinal spots, which are new living centres of growth 

 originating in living matter. In these are new centres, figs. 

 9, 10, n, and in these last others would have appeared at a 

 later period. In all cases the lifeless nutrient material must 

 pass into the very centre of the living particles, before the 

 peculiar vital properties are communicated to it. 



On the Production of Formed Material. The processes 

 of growth and increase, as they occur in the tissues of all 



* The cell wall (Huxley's "periplastic substance," regarded by him 

 as active and formative) is perfectly passive, while the germinal matter 

 (Huxley's endoplast of 1853, considered by him as unimportant) is 

 the really active and the only living matter of the cell. It is very 

 strange that Mr. Huxley should have so completely modified his views 

 upon this fundamental question, as he has done, without having offered 

 one word in explanation. 



