Nov. 14, 1889] 



NATURE 



39 



may be insured through an increase of mass in proportion 

 to a relatively diminishing surface nutrition. But such a 

 division would be much simpler than a process of karyo- 

 kinesis, and certainly than the formation of a new mouth 

 and a new anus. Here there is no question of a part (p. 73) 

 growing " to resemble the whole," comparable to the re- 

 growth, by crystallization, to replace a fragment broken 

 irom a crystal. We have a whole which divides itself in 

 such a way as to initiate and carry out a progressively 

 increasing difference— 2i difference between the two parts 

 dividing, and a difference (but a different kind of difference) 

 between each such part and the previously existing 

 whole. 



Passing from the consideration of the immortality of 

 Monoplastides to the mortality of Polyplastides, I cannot 

 see my way to accept the Professor's definition (p. 114) 

 of death : " An arrest of life, from which no lengthened 

 revival, either of the whole or any of its parts, can take 

 place,'' nor can I agree to his assertion {loc. cit.) that 

 death '•' depends upon the fact that the death of the cells 

 and tissues follows upon the cessation of the vital func- 

 tions .as a whole." If we cut up a Begonia plant or a 

 Hydra into small parts, such an individual Hydra or 

 Begonia cannot surely be considered as still alive, because 

 fresh Hydrce or Begonice may spring from such frag- 

 ments. Similarly with higher organisms, it would be pre- 

 posterous to say that a man was not dead because a 

 post-viorteni, inferior kind of life — such as can alone be 

 manifested in very lowly structures — was still persisting 

 in the cells of his tissues ! 



No doubt, as the Professor says, we cannot have death 

 without a corpse, but the tissues and cells of the corpse 

 may still retain a certain sort of life without the corpse 

 being any the less a corpse on account of that cir- 

 cumstance. 



But if life of some sort may be, as we agree, affirmed 

 of such cells, can we deny it absolutely (since no one 

 comprehends it) even to the molecules of the cells ? But 

 body-tissues of lower Vertebrates may retain such life for 

 a very long time. If, then, such a Vertebrate be devoured 

 by another animal, who would venture to affirm that it is 

 impossible that some of the micellae or tagmat?., or at least 

 the molecules of some of the cells of the creature devoured 

 may not pass, while still retaining a sort of life, into the 

 tissues of the devourer.'' Even tagmata must be small 

 enough to traverse the tissues, and can the possibility that 

 they may enter into their composition while still living be 

 dogmatically denied .' May we not affirm the certainty 

 of the death of the animal devoured till we are sure of 

 the impossibility of the survival of any of the molecules 

 of its cells ? 



No doubt the Professor would refer us to MagosphcEra 

 as presenting phenomena (so far as regards its cells) 

 which support his view. He says (p. 126) : — "The dis- 

 solution of a cell colony, with its component living 

 elements, can only be death in the most figurative sense, 

 and can have nothing to do with the real death of 

 the individuals ; it only consists of a change from a 

 higher to a lower stage of individuality. . . . Nothing 

 concrete dies in the dissolution of Magosphcera ; there is 

 no death of a cell colony, but only of a conception." But 

 surely it cannot be the same thing " to exist in a coherent 

 interrelated mass bound together by a common jelly," and 

 "to exist in separate parts, living independently without 

 interrelations, and not bound together by a common 

 jelly." If there is here "death of a conception," there 

 must be an external objective death corresponding there- 

 with. Magosphcera is a very lowly organism, and its life 

 can be very little better than that of a Monoplastid, 

 because its structure is very little more complex. It is 

 not wonderful, then, that there is very little difference 

 between its existence and the existence of its post-mortem 

 surviving cells. Yet the difference must be allowed to 

 ■be, however diverse in degree, like that in the higher 



animals. Let us suppose that half a dozen higher animals 

 could be so divided that no two cells remained in con- 

 tiguity, yet that every cell could retain 2. post-mortem life 

 such that by reuniting they could build up other indi- 

 viduals. Would it be reasonable to affirm that the higher 

 animals thus segmented had not been killed, or that when 

 their cells had reunited — possibly in very different com- 

 binations — the individual animals were the same ones as 

 before? An extreme illustration often best seems to bring 

 out the force and significance of a principle. 



The Ortho?iectides,\-ti&rre(\. to (p. 126) by the Professor 

 in controversy with Gotte, hardly illustrate the question 

 here discussed, but we note with much interest and satisfac- 

 tion that he is inclined to regard them as arrested larvJE, 

 Leuckart having found them ^ greatly to resemble the 

 new-born young of Distoina, as Gegenbaur has found 

 that the Dicyemids are like a stage in the development 

 of the Platyhelminthes. If this interpretation is, as it 

 probably is, correct, we have here an interesting example 

 of what we find in such Batrachians as Axolotl and 

 Triton a/pestris. 1 am inclined to look at illenobratichus, 

 Proteus, and Siren as larval forms which have now alto- 

 gether ceased to assume what was once the adult stage 

 of their existence- 

 Prof. Weismann's hypothesis concerning heredity is 

 certainly the best which has yet been proposed, but I 

 have not met with any reference to that proposed by Sir 

 Richard Owen forty years ago.* It is now out of date, 

 and his references are not of course expressly to "germ- 

 plasm," but to the contents of germ-cells. Nevertheless, 

 there is an undeniable resemblance between the two hypo- 

 theses, and any interested in Prof. Weismann's would do 

 well to read over Owen's small volume on the same 

 problem. 



But the complexity of Prof. Weismann's hypothesis is 

 such as to approach, if it does not even exceed, that of 

 pangenesis itself 



He tells us (p. 191): "Every detail of the whole organism 

 must be represented in the germ-plasm by its own special 

 and peculiar arrangement of the groups of molecules,' 

 and (p. 146) that " the number of generations of somatic 

 cells which can succeed one another in the course of a 

 single life, is predetermined in the germ.'' Moreover 

 none of these circumstances can be explained by any 

 difference of quality,'* but must be exclusively due to the 

 size, number, and arrangement of the component parts. 

 Now, if we consider what must be the complexity of con- 

 ditions requisite to determine once for all in the germ the 

 precise number of all the succeeding cells of epithelial 

 tissue, including every one of the rapidly succeeding cells 

 of glandular epithelium, and every blood corpuscle of the 

 whole of life ; to necessitate also every modification of 

 structure which may successively appear in polymorphic 

 organisms, which change again and again profoundly 

 between the &gg and the imago ; to arrange, at starting, 

 the successive very complex changes of arrangement 

 which must be necessary to build up reflex mechanisms 



I "Zur Entwicklungsgeschichte des Leberegels," .^f>o/. Anzci£;er, 1881, 



P- 99- 



' In this connection may be noted a pa^^sage which occurs on p. 26*5 of 

 Prof. A. C. riaddon's excellent introduction to the study of embyology. 

 Sollas is there quoted as saying that a longer mature life is possessed by 

 those forms which are " saved from the drudgery of a larval ex.stence." It 

 would be interesting to know whether Rana opisthodon is longer lived than 

 its congeners, s nee it has nj tadpole stage of life. 



3 See his work "On Parthenogenesis" (Van Voorst, 1849). There we 

 read: — "Not all the progeny of the primary impregnated germ-cell are 

 required for the formation of the body in all animals. Certain of its deriva- 

 tive germ-cells may remain unchanged and become included in the body 

 which has been composed of their metamorphosed and diversely combined or 

 confluent brethren ; so included, any derivative germ-cell or the nucleus of 

 such may commence and repeat the same processes," &c. (p. 5). At p. 68 he 

 speaks of " ihe retention of some of the primary germ-vesicles " Finally, on 

 p. 72, he says : — "' Ho* the retained spermatic force operates in the formation 

 of a new germ-process from a ^econdary, tertiary, or quaternary derivative 

 germ-cell or nucieiis, 1 do not profess to explain ; neither is it known how it 

 operates in developing the primary germ mass Irom the impregnated germ- 

 vesicle of the ovum. In both we witness centres of repulsion and of attraction 

 antagoQ z'ng to produce a definite result." 



4 P. loi, where the existence of "quality" is denied. 



