14 



POLYGASTRIA. 



The genus Chilodon presents a very simi- 

 lar organisation, but is remarkable from 

 the circumstance that its mouth is furnished 

 with a tubular fasciculus of setaceous teeth, 

 while the anterior part of its body is advanced 

 forward in the shape of an expanded membrane 

 or prolonged on one side, so as to form an 

 auriculated appendage. In Nassula, likewise, 

 a similar dental structure exists, but this will 

 be best described hereafter. 



Nutritive system. By employing coloured 

 organic substances as food for these animalcules, 

 Ehrenberg at length succeeded in developing 

 the organisation of the nutritive apparatus in 

 these microscopic beings. For this purpose 

 he made use of pure indigo, carmine, sap- 

 green, and other vegetable colouring substances 

 which are insoluble in but miscible with water, 

 very finely levigated, and which the animal- 

 cules readily swallow, so that in a few minutes 

 the coloured particles are distinctly visible in 

 the interior of their transparent bodies. 



From observations conducted in this manner 

 the following results were obtained : 1st. That 

 there is no absorption of the coloured fluid 

 through the general integument of the bodies 

 of infusorial animalcules, although this was 

 formerly supposed to be the only manner in 

 which they could be nourished ; but, on the 

 contrary, that they were all furnished with a 

 special mouth and internal nutritive apparatus. 



2nd. That the smallest species of Infusoria 

 which can be observed with our instruments, 

 even those not more than T ^ of a line in 

 length, have an internal set of nutritive organs 

 as well as the largest, so that in the Monads 

 even four, six, or eight sacculi are visible in 

 the interior of the body, which are obviously 

 filled through an oral aperture. 



In the genera Enchelis, Paramecium, and 

 Kolpoda, moreover, an intestiniform tube was 

 discovered traversing the whole length of the 

 body, and opening by a distinct anal orifice. 

 To this central canal are appended numerous 

 blind vesicles, giving the whole apparatus the 

 appearance of a bunch of grapes. In Para- 

 mecium aurelia and Paramecium chrysalis 

 Ehrenberg counted from one to two hundred of 

 these vesicles, which became filled with blue, 

 red, or green, according to the colouring matter 

 employed. 



We have, however, already, in the prece- 

 ding pages, described the different arrange- 

 ment of the alimentary canal in the va- 

 rious forms of polygastric animalcules, so 

 that few further observations are necessary in 

 this place. Whoever wishes to observe these 

 little beings swallow coloured food, and thus 

 witness the filling of the nutritive sacculi, must, 

 in order to avoid disappointment, carefully 

 observe that the materials he employs are per- 

 fectly pure, the indigo, carmine, and sap green 

 sold in the shops being generally so much 

 adulterated that the animalcules refuse to swal- 

 low it ; secondly, that it be reduced by leviga- 

 tion to the most extreme state of division 

 grinding it for a length of time with water on 

 a slab, with a muller, is the best way to ac- 

 complish this. When thus prepared, by placing 



a little with a camel's hair brush in the drop 

 of water which contains the animalcules, but 

 very few minutes are required with some species 

 to exhibit numerous vesicles filled with the co- 

 loured substance. When filled, Ehrenberg has 

 observed that sometimes one of them will in 

 a short time empty itself, and its contents be 

 suddenly transferred to another, whereby it 

 seems as if the vesicle itself had a power of 

 voluntary locomotion, which it has not. But 

 however easy it may be thus to fill the stomachal 

 vesicles, it is by no means so easy a matter to 

 detect the central canal to which they are ap- 

 pended, insomuch that the generality of ob- 

 servers are quite unable to detect its presence. 

 Upon this point Ehrenberg remarks, in reply 

 to those who have doubted its existence, that 

 there are only some animalcules in which it is 

 possible to see it clearly ; and it is therefore 

 necessary to seek out such species in order to 

 obtain a view of it. In many it is of all things 

 most difficult to see it ; but the cause of this 

 does not lie in its absence, but in the nature 

 of the functions it has to perform, for this canal, 

 like the oesophagus of larger animals, only 

 serves for the transmission of food, not for its 

 retention and digestion. It becomes dilated 

 while food is passing through it, at will, like 

 the mouth and oesophagus of a snake when it 

 swallows a rabbit, and immediately collapses 

 again, and becomes quite invisible when not 

 actually in use. 



Provided the indigo and carmine employed 

 for the purpose have been sufficiently levigated, 

 nothing is easier than to demonstrate the presence 

 of the stomachal vesicles; but to exhibit the 

 central canal, and the tubes that communicate 

 between it and the gastric sacculi, is a much 

 more difficult task, and can only be done under 

 very favourable circumstances. We were, in- 

 deed, long sceptical concerning their existence; 

 but after examining Professor Ehrenberg's pre- 

 parations of these structures, we were ulti- 

 mately convinced of the accuracy of his views 

 concerning them. 



Whoever wishes to see the intestinal tract 

 distinctly must examine it in large specimens 

 of some of the following species, most of 

 which are sufficiently common : Chelodon cu- 

 cullulus, Trachelius ovum, Epistylis plicatilis, 

 Vorticella chlorostigma, Vorticella convallaria, 

 Opercularia articulata, or Stylonychia mytilus. 

 On putting a little indigo into the water with 

 some of these, it may be readily seen to enter 

 their large mouths, and pass into their stomachs, 

 from which it is again speedily ejected. 



In the Monads and allied families the ali- 

 mentary apparatus consists of several distinct 

 cells, from eight to twenty in number, but 

 which are not all of them filled at the same 

 time. When contracted they are quite invisi- 

 ble; yet sometimes, when filled with a clear 

 fluid, they are to be distinguished under the 

 form of minute transparent vesicles in the in- 

 terior of the animalcule. The mouth may 

 sometimes be easily perceived under the form 

 of a clear transparent spot, situated at the base 

 of the proboscis, to and from which streams 

 of water may be seen to proceed, bringing 



