30 $ 1T. 
These movements succeed each other at more or less regular intervals. 
When these cavities are numerous, a certain order in the succession and 
alternation of their contractions cannot always be observed. It is very 
probable that their liquid contained during the diastole is only the nutri- 
tive fluid of the parenchyma, and to which it returns during the systole. 
In this way it has a constant renewal, and all stagnation is prevented. 
This arrangement constitutes the first appearance of a circulatory system, 
and the jirst attempt at a circulation of nutritive fluids. 
From an optical illusion similar to the one mentioned as belonging to 
the vacuole ($ 13) the liquid of these pulsating cavities has a reddish hue. 
INFUSORIA AND RHIZOPODA. 
§ 17. 
A round, pulsating cavity is found in the genera Vorticella, Epistylis, 
Loxodes, and in the following species: — Ameba diffluens, Paramecium 
kolpoda, Stylonychia mytilus, Euplotes patella, §&-c. With Actinophrys, 
Bursaria, Trichodina, there are from one to two; with Arcella vulgaris, 
three to four ; with Nassula elegans, there are four placed in a longitudinal 
line on the dorsal surface. With Trachelius meleagris, there is a series 
of eight to twelve upon the sides of the body, and with the various species 
of Amphileptus there are fifteen to sixteen arranged more or less regularly. 
With Stentor, there is a large cavity in the anterior portion of the body, | 
and many similar cavities appear upon the sides, united sometimes into 
one long canal. A similar canal traverses the entire body of Spzrostomum 
ambiguum, and Opalina planariarum. With Paramecium aurelia, the two 
round cavities present a remarkable aspect, being surrounded by five or 
seven others, small and pyriform, the top of which being directed outward, 
the whole has a star-like appearance.” During the pulsation, often the 
entire star disappears, sometimes only the two central cavities, and in some 
cases the rays only. 
These cavities, entirely disappearing in the systole, reappear in the dias- 
tole, and usually in the same place and with the same form and number. 
This would lead us to conclude that they are not simple excavations in 
parenchyma, but real vesicles ‘or vessels, the walls of which are so excess- 
ively thin as to elude the highest microscopic power. 
In some individuals, as, for instance, with Trachelius lamella, there 
appear, during the diastole, two or three small vesicles at the extremity of 
the body, which, after having increased in size, blend into one which is 
very large. These are probably only globules of nutritive fluid, separated 
from the parenchyma. Similar phenomena are observed in Phialina ver- 
micularis and Bursaria cordiformis. 
It sometimes happens with these animals that a forcible contraction of 
the whole body divides an elongated cavity into two spherical portions, as 
1 Ehrenberg (loc. cit. p. 321, Taf. XXXIII. fig. 
viii.), deceived by this illusion, has taken the eight 
totwelve contractile cavities of Trachelius melea- 
gris for stomachal cells, filled with red gastric juice. 
He has also regarded these cavities, when simple or 
double, as seminal vesicles. (Abhandl. d. Berliner 
Akad. 1833, p. 172,—1835 p. 168.) In species 
having but few, he has very arbitrarily decided that 
some are seminal vesicles, others stomachal pouches, 
as, for example, in Amphileptus (loc. cit. p. 355). 
A ding to him, the | vesicles, upon con- 
traction, pour the sperm upon the eggs contained 
in the body. It really seems very strange that 
* these animals should practise uninterruptedly these 
pollutions throughout their entire life. These ani- 
mals have neither testicles nor ovaries, and the 
function of these cavities is not, therefore, that 
‘assigned to them by Ehrenberg, —but is, as L 
think, with Wiegmann (Arch. f. Naturg. 1835, I. 
p. 12), analogous to that of a heart. 
1 Dujardin, ‘Ann. d. 8c. Nat. Zool. tome X. PL. 
XY. fig. 35 also, “Infusoires,” Pl. VIII. fig. 6. 
Ehrenberg’s plates of these star-like vesicles are 
incorrect. 
