256 DR. DUFFIN, ON PROTOFLASM. 
not shorten, but either retain their dimensions, or continue 
to elongate. Similarly the centrifugal current persists in a 
retracting filament. These experiments show the very shght 
consistence of the surface of the pseudopodia, that the move- 
ment of the granules may be compared to a current, and 
further they afford us a means of ascertaining what part of 
the animal is destined for the reception and digestion of 
nourishment. 
The consistence of the pseudopodia is, however, liable to 
considerable variations in different kinds of Rhizopods. The 
relation is the same as in the protoplasm of different cells or 
of the different parts of a cell. Among the Gromide the ex- 
tremes are best observed in G. oviformis and G. Dujardinii.* 
The latter is characterised by the completely hyaline cha- 
racter of the threads it emits. They are very torpid in their 
movements—so rigid and firm, as to show no tendency to 
flow together even on contact. They present no movement of 
their substance that can be compared with the granule 
motion, still there is no evidence of their being composed of 
loosely-aggregated threads. In G. oviformis, on the con- 
trary, the whole mass of the pseudopodia is uniformly gra- 
nular and diffluent. Many of the Miliolides occupy a position 
intermediate to the two varieties of Gromia. But even in 
the same animal firmer and more fluid hyaline and granular 
substance may occur together in the pseudopodia. Just as 
in many Ameebas a hyaline cortex encloses the granular in- 
terior, and the two constitute the Amceba, so there are pseu- 
dopodia the axis of which is a hyaline, and, it would seem, 
firm thread, on the surface of which the granular, softer ma- 
terial moves about. This is the case with <Actinophrys 
Kichhornii. The pseudopodia have so little movement that 
they look like hard spines; still they consist of a contractile 
material. Curves and coils are occasionally met with on them, 
and they possess the faculty of retraction, but all changes of 
shape occur very slowly. They are also endowed with the 
granule movement, but this is restricted to the cortical sub- 
stance. All the radiating filaments arise by means of their 
hyaline axis from the interior of the body of the animal, but 
the movable granular cortex comes distinctly from the 
cutaneous layer of the Actinophrys. It is further remark- 
able that several axial filaments, arising close together, but 
from distinct points on the medullary substance, may be 
apposed so as to constitute a common fibre. This union 
generally occurs during their course through the cortical 
* ‘Ueber d. Organismus d. Polythalamia,’ taf. i and taf. vii. 
