12 ANTHOZOA HYDROIDA. 



which, while it may remind us of the circulation in higher 

 animals, has yet hut little affinity with it ; and, according to 

 Van Beneden, as little with the circulation observable in the 

 stems of the Chara, with which it had been compared, for it 

 is not carried on in a closed tube or vessel.* The circulation 

 in question is that of a granulous fluid in the fistular stem of 

 the polypidom, and through every branch of it, and which 

 penetrates within the body and stomach of the polypes them- 

 selves. Cavolini discovered it first in the Sertulariae; and 

 soon after, in 1786, the celebrated Spallanzani observed 

 the same phenomenon, which he has described with great 

 particularity .f Miiller likewise noticed it in 1789, but mis- 

 took the moving granules for infusory animalcules. (Zool. 

 Dan. iii. p. 62.) Very recently the attention of naturalists was 

 more drawn towards the function by the observations of Mr. 

 Lister, who ascertained its existence in the Tubulariae, and in 

 almost all the genera of the order ; and subsequent researches 

 have done little beyond confirming what Mr. Lister has so 

 well described. 



* Mem. sur les Campanulaires, p. 17. 



f As Spallanzani's observations have been overlooked, I shall insert here his 

 account of them entire. He made the discovery in 1 786, and the truth of it he 

 confirmed, during his travels in the Two Sicilies, by new observations on a species 

 of Campanularia allied to C. volubilis. " Along the foot or stem," he says, " of every 

 polypus we see a small column or chain of particles which extend upwards to the 

 extremity of the bell. At first, I thought that these atoms made a part of the organiza- 

 tion of the animal ; but I afterwards found that they were not fixed but moveable, and 

 designed for the same function with the red globules of the blood in animals of a 

 superior order. The following is the method adopted by nature in the motion of 

 these minute particles. Every five or six minutes they ascended rapidly from the 

 bottom of the stem, and penetrated longitudinally through the middle of the bell. In 

 the mean time, the number of them in the stem diminished, until, at length, very 

 few remained there, the greater number having passed into the bell ; where they 

 were all in motion, producing a kind of eifervescence, which continued some seconds. 

 They afterwards returned, by the way they had ascended, to the lower extremity of 

 the stem, where they remained at rest for a short interval ; and during this interval 

 it was that I first saw them, and took them for a solid part of the animal. They 

 soon, however, resumed their former motion, ascending through the stem, and col- 

 lecting in the bell ; where the intestine ebullition again took place, till the current 

 again descended to the bottom of the stem, when the same alternation of rest and 

 motion succeeded. Thus the mass of these particles moved regularly and constantly 

 in the polypi, which it could not have done, unless we suppose a canal or longitudinal 

 vessel, though the transparency of the polypi prevented its cavity being discernible." 

 Travels in the Two Sicilies, iv. p. 287-9. 



