204 



NA TURE 



{July 12, 1877 



tions recorded on account of their discontinuity. Nothing 

 but a close and continuous observation of the same 

 forms extending over an entire Ufe cycle, repeated again 

 and again, can lead to absolute results. Errors fatal to 

 the interests of truth inevitably arise, when minute 

 organic forms are studied, not by continuous watching, 

 but from inferences made from the phenomena manilest 

 at different periods, the intervals between which are 

 blank. Further, whilst the use of reagents on the dead 

 forms taken at various stages is of the utmost value, when 

 they are examined side by side with continuous observa- 

 tion on the living form, these may be not only not instruc- 

 tive but misleading when taken by themselves. 



Butschli's observations are numerous and interesting, 

 but their value will be best estimated, by understanding 

 briefly the nature of the hypothesis they are declared by 

 their author to indicate. Put in its shortest form, it is 

 that conjugation amongst the Infusoria is simply a reju- 

 vi-ncsccHCC of the creatures which undergo it, enabling 

 them to become "the stem ancestors of a series of gene- 

 rations " which propagate by fission. As yet the process 

 of rejuvenescence has had, in biology, a limited applica- 

 tion, being noticed in the formation of the swarm-spores of 

 CEdogonium and other of the lowliest plants ; but its con- 

 nection with sexual reproduction is not clear, as no union 

 of different elements has been made out, and it is by no 

 means certain that the whole process of reproduction is 

 exhausted by it. When, however, it is combmed with 

 conjugation, as in the Bacillariace;e, it becomes plainer ; 

 although, so far as is known at present, it by no means 

 follows that the whole generative process in these forms 

 is known ; but it is to the Auxospores by which reju- 

 venescence is secured in these forms that Butschli appeals 

 for the support of his theory of infusorial conjugation. 

 Pfitzer and Schmitz have made what are at present the 

 most complete observations of the phenomena in question ; 

 from which we learn that the customary mode of reproduc- 

 tion is by fission, but at each repetition the individuals 

 dwindle in size,until they can apparently go no farther," then 

 the conjugation of two individuals takes place, the forma- 

 tion of auxospores being the result, that is to say rejuvenated 

 individuals ; and from these a new departure of fissiparous 

 generations takes place, well observed by Schmitz in 

 the case of cocconema cistiila. There is no coalescence ; 

 the frustules simply lay themselves parallel to one another, 

 they become surrounded by a common envelope of mucus ; 

 the protoplasm of the cells comes into contact, each 

 frustule grows larger and becomes an auxospore. What 

 the influence is which these frustules exert upon each 

 other is wholly unknown ; but that it has a real existence 

 is shown in the result ; each auxospore forming a stem 

 ancestor of a new series. 



This is what Butschli extends to the infusoria, and 

 contrary to the interpretations of Balbiani, Stein, and 

 others, maintains that the act of conjugation so well 

 known amongst. the Paramecia, Vorticell^e, &c., is not a 

 precursor of sexual products, but simply a means by 



I It is impossible not to notice hc.e the extremely interesting and cer. 

 tainly somewhat remarkable paper of Dr. Wallich m the February number 

 of the Monthly Microscopical Journal for 1877, " On the Relation between 

 the Development, Reproduction, and Markings of the Diatomacea: . for in 

 this p. per what is apparently the auxospore of PfiUer and Schmitz u called 

 the sporangialjrustule But this, instead of havmg dwindled in Size before 

 coniueati'in appears to have become enormous in proportion, and within this 

 the "new parents of the race arise," anJ from the conjugation of these the 

 new forms spring as daughter frustules. 



which these forms, exhausted by continued fission, become 

 more highly vitalised and rejuvenated, and .again enter 

 upon the process of fissiparous multiplication, which 

 indeed becomes thus their only method of increase. 



It should be noted that on the whole the facts adduced 

 by Balbiani and Stein are admitted, but they are sub- 

 mitted to a wholly different interpretation ; and it is 

 specially insisted on that the forms that go into the conju- 

 gation state are of a minimum size ; which fact Balbiani 

 explains as the result of a special development for sexual 

 purposes, but this is disallowed by Butschli, who insists 

 that it results from exhaustion of vitality at the terminus 

 of a series of fissiparous multiplications. Indeed these 

 weakened and minimised forms unite in conjugation 

 and are neither absorbed into each other nor produce 

 embryos, but increase in size and vitaHty, separate, and 

 commence again the fission by which alone increase is 

 effected. 



The truth of this is insisted on as deriving strong sup- 

 port from some of the very remarkable external changes 

 which the author has seen certain of the Infusoria 

 undergo. In Euplotcs and Oxytric/itnecr a great part 

 of the ciliary system is said to perish towards the end 

 of conjugation ; and afterwards, when stparation takes 

 place, to be again renewed. In Colpidiuin colpoda the 

 entire mouth was lost in conjugation, but was renewed 

 again after separation. So in Bursaria iruncatella, the 

 conjugated animals, it is affirmed, lose entirely the com- 

 plex apparatus of the peristoma, which by a new growth 

 after conjugation is restored. So also there is declared 

 to be a complete rejuvenescence of the more important 

 internal parts. The " secondary nucleus" \a Slylonichia 

 niytiliis, and in BUpharisina lateritia and Colpidium col- 

 poda the old nucleus is said to be eliminated and a new 

 one formed. In others, part of the nucleus is thrown off, 

 and part renewed ; in others a new nucleus formed and 

 coalesced with the old one. From these and similar 

 observations it is inferred that the " essence of conjuga- 

 tion consists in the rejuvenescence of both the indivi- 

 duals ;" and that this is chiefly centred in the ''secondary 

 nucleus " which is declared to be of the utmost importance 

 in the life of the creature. 



During the process of conjugation, also, the plasma- 

 contents of the individuals have been seen to interchange; 

 this especially in Oxytrichiitca; but also in other infusoria. 



Against Balbiani's hypothesis — that the nucleus is the 

 ovarium and the nucleolus the testis, containing spermatic 

 elements— Butschli affirms that in P. amclia and P. col- 

 poda the supposed spermatic capsule in some cases 

 wholly disappeared without any following change in the 

 nucleus that could be discovered, and that consequently 

 it did not effect fertilisation. In short, he believes that 

 the observations he has made are quit; competent to 

 overturn the sexual hypothesis in these organisms, and to 

 establish that of rejuvenescence in its place. 



That there is extreme ingenuity in this hypothesis we 

 readily admit ; that there is also the utmost conflict of 

 interpretation amongst the best observers of these orga- 

 nisms, we admit with equal readiness. But that the 

 author's observations give scientific sanction to his theory 

 on the one hand, or either explain away or harmonise the 

 I labours of his predecessors or collaborateurs on the other, 

 we are fain to dispute. The exhaustive and continuous 



