July I, 1875] 



NATURE 



177 



table kingdom, these, too, would' be referred without hesitation 

 either to the one or to the other, some passing to the former and 

 others to the latter. The group of the Protista is thus at beit 

 but a provisional one, based partly on our ignorance of the struc- 

 ture and life-history of the beings which compose it, and partly 

 on our inability to assign to the animal its essential difference 

 from the plant. Haeckel, however, has done well in specially 

 directing attention to it, and in his admirable researches on many 

 of the organisms which he has thus grouped together he has 

 largely contributed to our knowledge of living forms. 



I have thus dwelt at considerable length upon this important 

 paper of I lacckel's, because I think that it not only brings out in 

 a clear light the essential features of infusorial structure and 

 physiology as demonstrated by recent research, but that it goes 

 far to set at rest the controversy regarding the unicellularity and 

 multicellularity of the Infusoria. 



Balbiani has quite recently published a very interesting account 

 of the remarkable Infusorium long ago described by O. F. 

 Miiller under the name of Vorticella nassuta, and more recently 

 taken by Stein as the type of his genus Didinium. 



The animal, which is somewhat barrel-shaped, with an anterior 

 and a posterior wreath of cilia, has one end continued into a 

 proboscis-like projection which carries the oral orifice on its 

 summit, while an anal orifice is situated on the point diametri- 

 cally opposite to this. There is a very distinct cuticle, though 

 the rest of the cortical layer is very thin, and can scarcely be 

 optically distinguished from the internal parenchyma, which 

 exhibits manifest currents of rotation. These flow in a con- 

 tinuous sheet along the walls from the anal towards the oral side, 

 and on arriving at the mouth turn in towards the axis and then 

 flow backwards along this until they complete the circuit by once 

 morej reaching the anal side of the body. No trichocysts are 

 developed in the walls of the body. The contractile vesicle is 

 large, and is situated near the anal end ; it presents very distinct 

 pulsations, and Balbiani is disposed to believe in a communica- 

 tion between it and the exterior. 



During the act of digestion a tubular cavity can be seen run- 

 ning through the axis of the body, and connecting the oral and 

 anal orifices. This is regarded by Balbiani as a permanent diges- 

 tive canal. The post-oral or pharyngeal portion of this tube 

 possesses a very remarkable feature, namely, a longitudinal 

 striation caused by rigid rod-like filaments which are developed 

 in its walls, and which can be easily detached and isolated by pres- 

 sure or by the action of acetic acid. They then resemble some 

 common forms of the raphides developed in the cells of plants. 

 The function of these rods becomes apparent when the animal is 

 observed in the act of capturing its prey. The Didinium is 

 eminently voracious and carnivorous, and when in pursuit of 

 other living Infusoria, such as Paramecium, the prey may be 

 seen to become suddenly paralysed on its approach. A careful 

 examination will then show that the Didinium has projected 

 against it some of its pharyngeal rods, and to the action of these 

 bodies the arrest of motion is attributed. A curious cylindrical 

 tongue-like organ is now projected from the mouth towards the 

 arrested prey, to which it becomes attached by its extremity. By 

 the retraction of this tongue the prey is now gradually with- 

 drawn towards the mouth, engulphed in the distended pharynx, 

 and pushed deeper and deeper into the axial canal, where it is 

 digested, and the effete matter ultimately expelled through the 

 anus. 



From all this Balbiani concludes against the unicellular doc- 

 trine. He sees in the axial cavity a permanent alimentary canal, 

 and in the surrounding parenchyma a true perigastric space filled 

 with a liquid which corresponds with the perigastric liquid of 

 the polyzoa and of many other lower animals. He is not, how- 

 ever, disposed to make too broad a generalisation, and to insist 

 on the presence of an alimentary canal distinct from a body 

 cavity in all the other Infusoria. Here, however, he falls in 

 with the views of Claparede and Lachmann and of Greeff, and 

 maintains that as a rule the digestive and body cavity in the 

 Infusoria are confounded into a single gastrovascular system. 



Independently, however, of the untenableness of the concep- 

 tion of a united digestive and body cavity, it does not appear to 

 me that Balbiani makes out any case against the unicellularity of 

 the Infusoria. He admits that except in the pharyngeal and 

 anal portion there is no evidence of a differentiated wall in his 

 so-called digestive canal, and even though it be conceded that 

 the middle portion of this canal constitutes a permanent cavity 

 in the parenchyma, it would not differ essentially from other 

 lacunae permanently present in the protoplasm of many un- 



doubtedly unicellular organisms. It has been already remarked 

 that a communication between these lacunoc and the external 

 medium is paralleled in many simple cells, and these external 

 communications in Didinium present no feature essentially 

 different 



The phaiynx appears to be bounded by an inflection of the 

 cortical layer, and I believe we may regard the rod-like cor- 

 puscles here present as a pecuUar modification of the trichocysts 

 which in many other Infusoria are developed in the cortical layer 

 of the body. The projectile tongue-like organ is one of the 

 most remarkable features of Didinium ; we must know more, 

 however, than Balbiani has told us of it, before we can decide 

 on its real import. It is not improbably a pseudopodial exten- 

 sion of the protoplasm. 



Balbiani has followed the Didinium through the process of 

 transverse fission. This is preceded by the formation of two 

 new wreaths of cilia, between which the constriction and division 

 takes place, each half previously to actual separation developing 

 within it such parts as it had lost in the act of division. The 

 only part which in this act becomes divided between the two 

 resulting animals is the nucleus. The so-called nucleolus was 

 not seen by Balbiani, and though he observed two individuals in 

 conjugation by their opposed oral surfaces, he never witnessed 

 anything like the formation of eggs or embryos. 



I believe I have now laid before you the principal additions 

 which during the last few years have been made to our knowledge 

 of the Infusoria. But though it will be seen that the labourers 

 in the special field of microscopical research, to which I have 

 confined this address, have been neither few nor deficient in 

 activity, it must not be imagined that the subject has been ex- 

 hausted, or that many questions, more especially such as relate to 

 development, do not yet await Ae results of future investigations 

 for their solution. 



PRIZES OF THE FRENCH ACADEMY 

 AS our readers are aware, the Paris Academy of Science* 

 ■^ holds at the end of December each year a solemn meeting 

 for hearing eloges of the departed members, and deliver- 

 ing' prizes to the most deserving essayists. But owing to the 

 calamity of the war the prizes for 1873 were distributed in the 

 end of 1874, and the prizes for 1874 remained undistributed. 

 An extraordinary solemnity was celebrated on June 21, for the 

 distribution of the 1874 prizes, and henceforth we hope nothing 

 will prevent the Academy fulfilling its yearly duties with punc 

 tuality. M. Bertrand, the new perpetual secretary, read an 

 essay on the life and works of M. £lie de Beaumont, his prede- 

 cessor in the office. Since Abbe Duhamel, the first of these 

 perpetual secretaries, died, this has been the constant practice. 

 So Abbe Duhamel was praised by Fontenelle, Fontenelle by 

 Fouchy, Fouchy by Condorcet, &c. &c. But M. I^lie de Beau- 

 mont did not produce any iloge on Arago ; it will be the next 

 duty M. Bertrand will have to perform, and a very attractive one 

 it is. The following are the results of last year's competition as 

 announced at the meeting : — 



1. Grand Prize in the Mathematical Sciences for a Mathe- 

 matical Theory of the Flight of Birds was not awarded, 

 though 2,GOO francs were given to M. Penaud, the author of one 

 of the memoirs, and an "encouragement" of 1,000 francs to 

 the two authors of another memoir, MM. Hureau de Villeneuve 

 and Croce-Spinelli. 



2. This was also the case with the Grand Prize in the Physical 

 Sciences, the subject being Fecundation in Mushrooms. The 

 value of the prize was, however, divided between the authors of 

 two memoirs, viz., MM. Maxime Comu and Ernest Rose, and 

 M. Sicard. 



3. The Poncelet Prize in Mechanics was awarded to M. 

 Bresse, Engineer-in-chief des Ponts et Chaussees, for his work 

 entitled " Cours de Mecanique Appliquee," and particularly for 

 the great progress shown in the part devoted to the resistance of 

 materials. 



4. The Montyon Prize in Mechanics to M. Peaucellier, 

 Lieutenant- Colonel of Engineers, for his researches on the trans- 

 formation of alternate rectilineal motion into alternate circular 

 motion. 



5. The Plumey Prize to M. Joseph Farcot for his setvo-moteur, 

 or moteur-asservi, an apparatus which renders the action of the 

 rudder more certain and more easy. 



6. The Lalande Prize in Astronomy is a sextuple one, and 

 was divided among MM. Mouchez, Bouquet de la Grye, 



