136 



NATURE' 



\yune 17, 1875 



The additions to the Zoological Society's Gardens during 

 the past week include a Grant's Gazelle {Gazdla granti) from 

 East Africa, presented by Dr. Kirk ; a Beccari's Cassowary 

 {Casuarius heccarii) from New Guinea, presented .by Sir James 

 Fergusson ; an Owen's Apteryx {Apieryx cnoeni), two Weka 

 Rails {Ocydromus australis), a Black Wood Hen {Ocydromus 

 fuscus), from New Zealand, presented by Dr. G. Hector ; two 

 Australian Cranes [Grus australaiiana) from Australia, pre- 

 sented by the Acclimatisation Society of Wellington, New Zea- 

 land ; a Brown Indian Antelope ( Tdraceros subquadruornidus) 

 from India, a Dufresne's Amazon {Chrysotis dufresniand) from 

 South-east Brazil, four Vulturine Guinea Fowls {Nuniida vultu- 

 rind) from East Africa, an Anaconda {Eunectes murinus) from 

 South America, purchased. 



RECENT PROGRESS IN OUR KNOWLEDGE 



OF THE CILIATE INFUSORIA"^ 

 T BELIEVE that the object contemplated by the addresses 

 which it has been the custom of your Presidents to deliver year 

 after year to the Fellows of the Linnean Society will be best 

 fulfilled by making them as much as possible the exponent of 

 recent progress in biological science. The admirable addresses 

 with whicti my distinguished predecessor has during his long 

 tenure of office so greatly enriched our journal, afford an example 

 as regards the exposition of botanical research which may well be 

 followed in biology generally. The field, however, which thus 

 offers itself is so wide, the activity in almost every department so 

 intense, that the necessity of restricting the exposition within a 

 limited area becomes imperative if it be expected to produce 

 anything like a definite picture instead of a vast assemblage of 

 images confused and ill-defined by their very multiplicity and by 

 the condensation which would be inseparable from their 

 treatment. 



While thus imposing on myself these necessary limits, it is 

 almost at random that I have chosen for this year's address some 

 account of the progress which has recently been made in our 

 knowledge of the Ciliate Iisfusoria— a group of organisms 

 whose very low posiiion in the animal kingdom in no way lessens 

 their interest for the philosophic biologist, or their significance in 

 relation to general morphological laws. 



To enable you to form a correct estimate of the value of recent 

 researches, it may be well to bring before you in the first place, 

 as shortly as possible, the chief steps which have led up to the 

 present stand-point of our knowledge of these organisms. 



It is scarcely necessary to remind you that the first important 

 advance which during the present century was made in our know- 

 ledge of the Infusoria dates from the publication of the great 

 work of Ehrenberg, * whose unrivalled industry opened up a new 

 field of research when, by his expressive figures and well-con- 

 structed diagnoses, he made us acquainted with the external 

 forms of whole hosts of microscopic organisms of which we had 

 been hitherto entirely ignorant, or which were known only by 

 such figures and descriptions as the earlier observers with their 

 very imperfect microscopes were able to give us. 



Ehrenberg, however, as we all know, did not content himself 

 with pourtraying the external forms of the microscopic organisms 

 to whose study he had devoted himself, but sought also to deter- 

 raine their internal structure, of which scarcely anything had 

 been hitherto known. In this direction, no less than in the other, 

 the perseverance of the celebrated microscopist never flagged ; 

 but, unfortunately, at the very commencement of his researches 

 he slid into a misleading path, and was never again able to find 

 the right one. 



Everyone knows how Ehrenberg, in accordance with precon- 

 ceived notions of the high organisation of all animals, attributed 

 to the Infusoria a complicated structure ; how, while he rightly 

 distinguished them from the Rotiferse with which they had been 

 confounded by previous observers, he yet regarded them as 

 intimately related to these representatives of a totally different 

 type ; and how, in attributing to them a complete alimentary 

 canal with numerous gastric offsets, he took this feature as their 

 most important character, and designated them by the name of 

 Polygastrka. And it is probably a matter of surprise to many 

 of us, that with the overwhelming mass of evidence which sub- 

 - sequent research has brought to bear against the truth of the 



T * Anniversary Address to the Linnean Society, by the President, Dr. G. 

 J. Allman, F.R.S., May 24. 



t " Die Infusionsthierchen als voUkommene Organismen." Leipzig, 1838, 



polygastric theory, the great Prussian observer should still adhere 

 with undiminished tenacity to his original views. 



Among the authors who, since the publication of the " Infu- 

 sionsthierchen " have contributed most to a correct estimate 

 of the morphology, physiology, and systematic position of the 

 Infusoria, the names of Von Siebold, Stein, Balbiani, Claparede, 

 and Lachmann, and most recently, Haeckel, stand out con- 

 spicuous. 



The first who from a strong position offered battle to the 

 authority of Ehrenberg was Carl f heodor von Siebold. * Von 

 Siebold rejected in toto the polygastric theory, and, so far from 

 admitting a complexity in the organisation of the Infusoria, he 

 regarded them as realising the conception of almost the very 

 simplest form of life, and attributed to them the morphological 

 value of a cell. 



Let us see what is involved in this most significant comparison. 

 The essential conception of a cell is, as you know, that of a more 

 or less spherical mass of protoplasm with or without an external 

 bounding membrane, and with an internal nucleus or differen- 

 tiated and more or less condensed portion of the protoplasm. It 

 was to a form of this kind that Siebold compared the body of an 

 Infusorium. He called attention to the soft protoplasmic mass 

 of which the body mainly consists ; to the external firmer layer 

 by which this is surrounded ; and to the variously-shaped body 

 differentiated in the protoplasm, to which Ehrenberg had gra- 

 tuitously attributed the function of a male generative organ. 

 Here then were, according to Siebold, the protoplasm body sub- 

 stance, the bounding membrane, and the nucleus of a true cell. 



The morphological value thus attributed to the true Infusoria 

 — under which were included the Flagellatse — was extended by 

 Siebold to Amoeba and its allies, and to the whole assemblage 

 so constituted he assigned the position of a primary group of 

 the animal kingdom to which he gave the name of Protozoa, 

 whose essential chiracter was thus that of being unicellular 

 animals. He then divided his Protozoa into those which had the 

 faculty of emitting pse-.idopodial prolongations of their protoplasm 

 (Amoeba, &c.), and those in which the place of the pseudopodia 

 v/as taken by vibratile cilia or by lash-like appendages. To the 

 former he gave the name q{ Rhizopoda ; to the latter he restricted 

 that of hifiisoria ; and lastly he divided the Infusoria into the 

 mouth-bearing, Stomafoda (Ciliata), and the mouthless, Aiiomata 

 (FJagellata). From every point of view Von Siebold's concep- 

 tion of the morphology of the Protozoa, and his sketch of their 

 classification, however much this may have been subsequently 

 modified, must be regarded as marking out an epoch in the 

 history of zoology. 



Shortly after this the unicellular theory was strongly supported 

 by Kolliker,t and received further confirmation from the re- 

 searches of Stein,J who, however, was unable to accept it to its 

 full extent. With an industry almost equal to that of Ehrenberg, 

 Stein had the advantage of the more philosophic views of organi- 

 sation which had emanated from the newer schools of biology, 

 and to him we are indebted not only for more accurate views of the 

 structure of the Infusoria, but for the first important contributions 

 to our knowledge of their development ; and though the opinion 

 which he at one time entertained, that the true Acinette are only 

 stages in the development of the higher Infusoria, has been aban- 

 doned by him, he has nevertheless demonstrated the presence in 

 an early period of the development of certain species, of peculiar 

 pseudopodial processes resembling the characteristic capitate 

 appendages of the Acinetse, an observation of importance in its 

 bearing on the relations of these last to the true Infusoria. No 

 doubt can remain, after Stein's observations, that the Infusoria 

 in their young state have the morphological value of a simple 

 cell, and it is only after their development has become advanced, 

 and that a marked differentiation has begun to manifest itself in 

 this primordial condition, that there can be any difficulty in 

 accepting their absolute unicellularity. 



About this time Balbiani drew attention to some very im- 

 portant phenomena in the life history of the Inftisoria.§ It had 

 been known even to the early observers that the Infusoria multi- 

 plied themselves by a process of spontaneous fission. They had 

 been frequently observed in the act of transverse cleavage, and 

 had also been noticed in what appeared to be a similar cleavage 

 taking place in a longitudinal instead of a transverse direction. 

 Balbiani, however, showed that this apparent longitudinal 



* Siebold, "Lehrbuch der vergleichenden Anatomie," 1845. 

 t i^eitschr. f. Wissens. Zool., 1849. 

 t Stein, "Der Oreanismus der Infusionsthiere," 1867. 

 § Balbiani, " Recherches sur les organes generateurs et la reproduction 

 des Infusoires." Comj>tes Rendus, 1858, p. 383. 



