344 pROF. EHRENBERG ON ANIMALS OF THE CHALK. 
lar to those which the marine Gasteropodes (Strombus, &c.) ex-— 
hibit, clustered racemosely, and also some Bryozoa fastened — 
singly to the exterior of their shell, which I also had observed in 
Stylaria proboscidea, but which have never yet occurred in any 
Infusorium. They are secreted small and soft; then swell very 
much in water (just as frog spawn), and harden. I have kept 
two of these forms with egg-cells well preserved, dried, in my 
collection. 
Besides these positive characters, I have taken great pains to 
deduce with some certainty a negative one; it is the non- 
existence of pulsating vessels. In all mollusks, even in the 
very minute Aggregati s. Ascidii compositi, I have always di- 
stinctly observed these pulsations above many other far coarser 
parts of organization; but they are evidently wanting in the 
above-mentioned two genera of Polythalamia. Now this ob- 
served deficiency removes for the present all the Polythalamia 
decidedly from the proximity of the mollusks and articulated 
worms, and places them in the series of the pulseless gangliated 
animals, or invertebrate vascular animals (Ganglioneura asphycta), 
although the nervous mass and the vascular system have not yet 
been ascertained. The other characters already communicated 
to the Academy in 1838, together with the position in the na- 
tura! kingdom there given, are only confirmed and established 
by these subsequent observations ; and the notion, recently trans- 
ferred from the Infusoria, which had outgrown these ideas, to 
the Polythalamia, of an animated simple organic substance oc- 
curring here and there, is hence likewise less and less supported 
by the experience which becomes daily more extended *. 
* M. Dujardin has this last August, in a Mémoire sur une classification des 
Infusoires en rapport avec leur organisation, laid before the French Academy a 
new arrangement of the Infusoria, in which he has again placed the Polythalamia 
as Rhizopoda, in the same order with Amoeba and Actinophrys of the Infusoria, 
and merely retained them in a separate family. But if the anatomical and phy-— 
siological details of the different organs deserve the least attention as to their 
general arrangement and systematic distribution, and mere external relations 
of form be not alone considered as of value, then this classification, where fee 
culiar, is often not to be considered successful. M. Dujardin has not demon- 
strated the polygastric structure of the Rhizopoda, indeed no structure at all ; ~ 
and that it is not polygastric, will again be evident from the investigation now ~ 
communicated of other groups of these bodies. Moreover, this diligent author — 
has given new names and characters to many things well known and charac- 
terized long before, which, at some other opportunity, will be more specially 
pointed out and adjusted. 
[To be continued. ] 
