divisions. The right and clear comprehension of the pur- 

 pose of this process, or the object effected by it, is essential 

 to the elucidation of the nature and relations of the sub- 

 sequent modifications and varieties in the course of deve- 

 lopment. The progeny of the c primary impregnated 

 germ-cell * may be called e secondary ' or e derivative 

 impregnated germ-cells/ and the whole is the 'germ- 

 mass. 3 



The progeny of the impregnated germ-cell resemble 

 their parent, with a diminution of size, to a certain stage of 

 descent, when they may be ultimately reduced to their es- 

 sential parts or nuclei (fig. 11). "When they cease to exist as 

 germ-cells or nuclei of such, either by coalescing with others 

 or by liquefaction, they do not lose their vitality : as indivi- 

 duals, indeed, they may be said to die, but by their death 

 they minister to the life of a being higher than themselves 

 (e.g. figs. 12, 13). They combine to construct its tissues 

 or dissolve and impart properties to its fluids ; these me- 

 tamorphoses being mysteriously governed by a plastic 

 nature or mode of force operating unconsciously upon the 

 matter, but according to a law of order and harmony, and 

 to a fore- ordained and definite end, resulting in a distinct 

 and specific form of animal adapted by its organization for 

 a particular sphere of existence, and forming a more or less 

 valuable, but not, as once was thought, an essential link 

 in the great chain of organic life. 



Not all the progeny of the primary impregnated germ- 

 cell are required for the formation of the body in all animals : 

 certain of the derivative germ-cells may remain unchanged 

 and become included in that body which has been composed 

 of their metamorphosed and diversely combined or confluent 

 brethren : so included, any derivative germ-cell or the nu- 

 cleus of such may commence and repeat the same processes 

 of growth by imbibition, and of propagation by sponta- 

 neous fission, as those to which itself owed its origin ; fol- 

 lowed by metamorphoses and combinations of the germ- 



