Mr. H. J. Carter on the Organization of Infusoria. 283 



takes place, the fundus of the bottle is forced into the interior 

 of the Paramecium, while, when the systole takes place," the 

 fundus moves towards the papilla, or externally. Now, if the 

 vesicula was not for ejecting the fluid which it receives from the 

 sinuses and their vessels, but, on the contrary, for returning it 

 into them, why should it have a distensible neck, this neck be 

 attached to a papilla on the surface of the body, and the line of 

 direction in which the vesicula contracts be from the fundus to 

 the papilla ? 



MM. Claparede and Lachmann state that no current can be 

 seen to pass out at the papilla in the Infusoria, and in this they 

 are right; but why ? simply because it is impossible to see this 

 without adding some colouring matter to the water, and then 

 the particles are whirled off the surface of the animalcule by its 

 cilia with such rapidity and confusion, that it is equally impos- 

 sible to discover among them the drop of fluid which may be 

 ejected from the vesicula. But let us take an organism closely 

 allied to the Infusoria, and not covered with cilia, that we may 

 see what takes place there. This brings me to Cohn's statement 

 above mentioned. 



I must now assume that the vesicula or contracting vesicle, 

 its sinuses and its vessels, are the homologue of this system in 

 the Rotatoria ; but not having been able to get Brachionus mili- 

 taris, I must take Brachionus urceolaris, which has no sinus 

 connected with its vesicula, a matter of no consequence here. 



The system in B. urceolaris consists of a vesicula connected 

 with a set of vessels on each side, which are more or less branched 

 and terminate in blinded extremities, and a few monociliated 

 appendages which are attached to them. In Paramecium, where 

 the system is double, each part consists of a vesicula, sinuses, 

 and more or less branched vessels, which also end in blind ex- 

 tremities. Thus the monociliated appendages do not appear in 

 Paramecium, nor the sinuses in Brachionus. With these excep- 

 tions, equally matters of no consequence here, there is such a 

 similarity in every part of these systems in Brachionus and Para- 

 mecium, that it seems to me no reasonable doubt can be enter- 

 tained that they are homologous. 



Now, what is witnessed when we place Brachionus urceolaris 

 in water with which colouring matter has been mixed (say fine 

 Indian ink), under a slip of glass which so compresses the Bra- 

 chionus as to keep it stationary and prevent the coloured fluid 

 from getting between it and the eye of the observer ? We see 

 that the vesicula becomes filled with a transparent colourless 

 fluid, and that this fluid, as the vesicula contracts, is suddenly 

 forced out of the cloaca into the surrounding medium, where, 

 for a moment or two, it remains unmixed with the coloured 



