118 Mr. H.J. Carter on the Circulation of the 



connected with a set of vessels something hke those of Para- 

 mecium aurelia^. 



The individuals which become encysted in the internode of 

 Nitella I have never been able to see clearly, on account of their 

 rapid movements and gorged state with the green disks (fig. 1) j 

 but the depression indicating the position of the mouth can be 

 seen, and two contracting vesicles. After the segmentation, 

 which stops at 2, 4, or 8, and full development of the new brood 

 has taken place, the green matter, now become brown, is thrown 

 off as effete (figs. 3, 5), like that of the '' globular vesicles '' 

 after the monads appear, and the cysts giving w^ay, the new in- 

 fusoria come forth, presenting the arrangement of cilia, form of 

 nucleus, and colour of Otostoma (fig. 5) ; but there is only one 

 contracting vesicle at this time, and the mouth is not so rigidly 

 fixed or defined as in Otostoma, probably from the tender age of 

 the new animalcule. 



During the process of segmentation, the external and internal 

 cysts at first appear to be newly secreted, and the old ciliated 

 integument to be divided up into coats for the new litter ; but 

 this does not correspond with what has been before stated, 

 where the old coat seems to be metamorphosed into a cyst- 

 covering for the new litter, and another delicate cyst secreted 

 within this (figs. 2, 3) ; while the internal substance then di- 

 vides itself up into 2, 4, or 8 sacs, as the case may be, and each 

 division developes a new ciliated coat for itself (figs. 3, 4). 



The presence of a few monads, which probably formed part of 

 the contents of the internode before they were gorged by the 

 infusorium, and retained their life by getting between the cysts 

 (fig. 3 b, h)y favours the view that the external cyst was the 

 originally ciliated coat of the parent infusorium. 



Lastly, I have to give an explanation of the locomotive power 

 afforded to the fragments of the spiral bands of " Zygnema '^ 

 mentioned at p. 16, which I now feel convinced did not derive this 

 power from their own mucus, but from having been enclosed 

 within the bodies of delicate Amoebce, which afterwards crept 

 about under the radiated form of Actinophrys. 



Circulation. 



It has been shown above, that rhizopodous cells abound in 

 the mucus-layer of the old internode of Nitella, but at a very 

 early period do not appear in the internodes or roots of the 

 young plant. Hence it becomes necessary to adduce further 



* In a future communication, I propose describing this "system of 

 vessels," which are excretory at the contracting vesicle ; when I shall also 

 recur to the description of Otostoma more particularly. 



