The Cambridge natural history, Vol. 01 (of 10)Hickson, Sydney J. (Sydney John)
Science
The Cambridge natural history, Vol. 01 (of 10)
Hickson, Sydney J. (Sydney John)
Animals
The _pseudopodia_ are long and radiating, with a granular external layer,
whose streaming movements are continuous with those of the inner network.
In the Acantharia they contain a firm axial filament, like that of the
Heliozoa, which is traceable to the central capsule; and occasionally a
bundle of pseudopodia may coalesce to form a stout process like a flagellum
("sarcoflagellum"). Here, too, each spine, at its exit from the jelly, is
surrounded by a little cone of contractile filaments, the _myophrisks_,
whose action seems to be to pull up the jelly and increase the volume of
the spherical body so as to diminish its density.
[Illustration: FIG. 25.—Skeletons of _Radiolaria_. A, _Dorataspis_; B,
_Theoconus_. (After Haeckel.)]
The _intracapsular protoplasm_ is free from _Zooxanthella_ except in the
Acantharia. It is less abundantly vacuolated, and is finely granular. In
the Porulosa it shows a radial arrangement, with pyramidal stretches of
hyaline plasma separated by intervals rich in granules. Besides the alveoli
with watery contents, others are present with albuminoid matter in
solution. Oil-drops, often brilliantly coloured, occur either in the plasma
or floating in either kind of vacuole; and they are often luminous at
night. Added to these, the intracapsular plasm contains pigment-granules,
most frequently red or orange, {81}passing into yellow or brown, though
violet, blue, and green also occur. The "phaeodium,"[89] however, that
gives its name to the Phaeodaria, is an aggregate of dark grey, green, or
brown granules which are probably formed in the endoplasm, but accumulate
in the extracapsular plasm of the oral side of the central capsule.
Inorganic concretions and crystals are also found in the contents of the
central capsule, as well as aggregates of unknown composition, resembling
starch-grains in structure.
In the Monopylaea, or Nassellaria (Figs. 25, B, 26, A), the endoplasm is
differentiated above the perforated area of the central capsule into a cone
of radiating filaments termed the "porocone," which may be channels for the
communication between the exoplasm and the endoplasm, or perhaps serve, as
Haeckel suggests, to raise, by their contraction, the perforated area: he
compares them to the myophane striae of Infusoria. In the Phaeodaria (Fig.
26, B), a radiating laminated cone is seen in the outermost layer of the
endoplasm above the principal opening ("astropyle"), and a fibrillar one
around the two accessory ones ("parapyles"); and in some cases, continuous
with these, the whole outer layer of the endoplasm shows a meridional
striation.
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account