50 BENNETT^ ON THE MOLECULAR THEORY, 



molecules wliicli, on receiving the stimulus it imparts, assumes 

 the power of growth. It is the same among the Phanero- 

 gamia, when the germ-cell is impregnated by the pollen- 

 tube. In all these cases it is necessary to remember that 

 the protoplasm is a mass of molecules ; that a spore is another 

 mass of molecules ; that sporules are molecules ; that anthe- 

 rozoids are only molecules with vibratile appendages ; and that 

 the so-called germinal matter of the ovule is also nothing but 

 a mass of molecules. Cell-forms are subsequent processes, 

 and once produced may multiply endogenously, by gemmation 

 or cleavage ; all that is here contended for is that the primary 

 form is molecular, and that the force-producing action in it 

 is a molecular force. 



In animals, as in vegetables, every primary act of genera- 

 tion is brought about by the agency of molecules. The 

 Protozoa entirely consist of mere molecular, gelatiniform 

 masses, in which it has never been pretended that a cell- wall 

 or central cell exists. And yet such masses have the power 

 of independent motion and of multiplying by gemmation. 

 Considerable discussion has occurred as to whether, among 

 Infusorians, there is a union of sexes or a conjugation 

 similar to what occurs among the Protophytaj but in either 

 case it is by molecular fusion that the end is accomplished. 

 In the higher classes of animals there are male elements, 

 consisting of molecules, generally with, but sometimes 

 destitute of, vibratile filaments, and female elements, com- 

 posed of the yolk within the ovum, containing a germinal 

 vesicle or included cell. Both spermatozoid and germinal 

 vesicle are dissolved in the molecules of the yolk, which then, 

 either wholly or in part, by successive divisions and trans- 

 formations, constitute a germinal mass out of which the 

 embiyo is formed. Here, as in plants, it is necessary to 

 remember that the spermatozoids, the yolk, and the germinal 

 mass, are all composed of molecules, and that these, combining 

 together, form the nuclei, cells, fibres, and membranes which 

 build up the tissues and organs of the organism. It is not 

 from either the male or the female element that the embryo 

 is formed. The supporters of an exclusive cell doctrine have 

 endeavoured to show that there is always a direct descent 

 either from the wall of the ovum or from the germinal 

 vesicle as its nucleus. Thus, some consider that the vitelline 

 membi'ane sends in partitions to divide the yolk mechanically. 

 Others have formed the idea that the germinal vesicle bursts, 

 and that its included granules constitute the germs of those 

 cells which subsequently form in the germinal mass. Others, 

 again, suppose that on impregnation the germinal vesicle 



