44 



plasm possess the power of reproducing the whole animal, or the head end 

 or the tail end, according to circumstances ? If the germ- plasm is con- 

 cerned in these restorations of parts, we can hardly exclude it from other 

 cases of restorations, and this will lead us to the admission that germ- 

 plasm is present in nearly all the tissues of all animals. If the position 

 is taken that the germ-plasm is not concerned in the cases that have been 

 referred to, but some degraded product of germ-plasm, then we may say 

 that such materials have powers curiously similar to those of germ-plasm 

 itself, but even more wonderful. To what extent is the material of the 

 cells of the cut surface of the worm different from that of germ-plasm 

 itself, when those cells have the inherited power to produce either head 

 or tail as demanded by the needs of the worm? If the molecular struct- 

 ure of germ-cells and of body-cells is so similar, is it impossible that some 

 of the body-cells may undergo retransformation into germ-cells? Further- 

 more, whether this suppositious reproductive material is or is not con- 

 cerned in the restoration of the minced hydra it must, if it exists at all, 

 be present in all the cells. For, so far as we may judge, each hydra that 

 has grown from a minute bit of hydra is capable of giving origin, when 

 divided, to many new hydras, and these to others indefinitely. Since the 

 last of such a series would, without doubt, be able to produce eggs the 

 germ-plasm must have been contained in all the cells of all the series. 



Weismann's conception is that the highly organized germ-plasm found 

 in the nucleus is, after the first division, no longer what it was before, 

 except that part which has been reserved, — is indeed no longer germ-plasm 

 at all. At each subsequent division its structure becomes simpler as it 

 gives origin to more and more complex tissues ; that is, its energy runs 

 down as it does work in forming tissues. He claims that, when the germ- 

 plasm has thus become simplified, its character as germ-plasm can never 

 be restored. It might be supposed that, if we could find any cells which, 

 having once formed a part of any body-tissue, should take upon itself the 

 powers of a reproductive cell, "Weismann's theory would stand disproved. 

 We then direct attention to the somatic cells of hydroids Avhich develop 

 into eggs. But Weismann accounts for this by supposing that the germ- 

 plasm enters the cells and takes the place of the germ-plasm. 



However, it appears to me that it must be admitted that the germ- 

 plasm is so widely diffused through the tissues of many, if not all, organ- 

 isms, and is so much like the substance of many other cells in its repro- 

 ductive powers, as to make it doubtful whether there is any such dis- 



