SCIENTIFIC SUMMARY. 
289 
may be farther classified according as the gills are seated on one or 
other point of the surface, thus : — Epibranchia, when these organs are on 
the back (Doris, etc.) ; Peribranchia, when they are placed round the mantle 
(Glaucus, etc.); Hypobranehia (same as the old Inferobranchia) ; and 
Pleurobranchia, when they are placed upon the side, as in Pleurobranchus, 
etc. The order Stegibranchia is also divided into four sections : first the 
Stegibranchia proper (corresponding to Cuvier’s Tectobranchia minus , the 
Pleurobranchs, and to the Scutibranchs of the same author) ; second, the 
Cyclobranchia, which are the same as Cuvier’s ; third, the Heteropod 
Stegibranchia, which, like Carinaria, have the heart and branchiae beneath a 
minute shell ; and finally the Ianthinae, which have the gills semi-detached. 
The order Endobranchia corresponds pretty closely to the Pectinibranchs 
and Tubulibranchs, and is subdivided into two groups, the Turbinge and 
Tubulae. Each of the preceding orders is so related to the other, that in a 
schematic arrangement it would be impossible to group them in one line, 
or even in two or three parallel lines ; they should be placed one at each 
angle of a triangular figure. Were it not for Blainville’s suggestion that 
some gastropods should rank among the Acephala, the term Cephalidia 
might advantageously be substituted for that of Gastropoda. — Comptes 
Rendus , vol. lvii. No. xx. 
Vitality of Rotifers. — It has been frequently stated in works on physio- 
logy and comparative anatomy that wheel animalcules may be completely 
desiccated and allowed to remain in that condition for an immense period 
of time, at the end of which, if a few drops of water be thrown upon 
them, they are immediately resuscitated. M. Pouchet says, that if this be 
true, then the school of physiologists which believes that life is the result 
of the operation of the physico-chemical forces will have much to support 
it. He, however, denies that such vitality is preserved by rotifers, and 
supports his denial by the following experiments : — A series of tubes, two 
decimetres long and eight millimetres in diameter, and capable of containing 
ten cubic decimetres of air, w r ere taken. After being dried, there were intro- 
duced into each tube two decigrammes of earth which had been taken from 
a dry spot and exposed for ten days to the sun, and for ten other days to 
the vacuum of a receiver. Each tube contained about fifty rotifers and 
eight tardigrades which were alive at the period of commencing the experi- 
ment. The tubes were now closed with the blow-pipe, and in some of 
them there had been placed small particles of lime, which were separated 
from the earth by a fold of cotton. One series of tubes, which had been 
exposed during the six hottest months of the year to the noonday sun, was 
when broken found to contain not a single living animalcule ; and, to judge 
from the shrivelled condition, the creatures must have been dead for some 
considerable time. A second series, containing lime, gave the same results 
in four months’ time. Finally, when the animalcules were dried by more 
powerful physico-chemical agencies, the same result followed. M. Pouchet 
observes : “ Observation and experiment unite in proving that the hypo- 
thesis of resurrections which w r as equally the wonder and amusement 
of the physiologists of the last century, should not find serious advocates 
in ours : like the doctrine of enclosure of germs, it has had its day.” — 
Comptes Rendus , November 20. 
