the polymei*izstion of' simple carbohydrates to more complex polysaccharides.
The prwise role of' t h e two types of rcinoehocyte is difficult to define
and there is little in the litcrature to enable firm conclusions to be
reached. I h t h thr hyaline mid the granular amoebocyte are reported
to be phagovytic and tlhe former has considerable powers of amoeboid
movement. Azbma (1!)37) has drawn attention to the fact that the
distinction bctween these two anioebooytcs is not always clear and that
in fact, they may be different stages of a single cell type. The strongly
amoeboid prol)ertirs of thv hyaline type may be associated with
phagocytic activity, while the less mobile mature granular cell may be a
contrasting metabolic phase. In any event it seems likely that both
types are cwiccmied in some way with the basic nutrition and metabolism of the imimal ; modern tmhniques in biochemistry should be able
to throw more light, on this problcm. Kalk (196313) believed that the
hyaline amoeboc*yte phagocytizes beads of vanadium-laden mucus in
the pharynx and gives rise to vacuolar amoebocytes and signet-ring
cells.
Both thc nephrocyte and the orange pigment cell appear to be
depositories for metabolic waste products. The absence of certain
uricolytic enzymes results in incomplete metabolism of purines and
related compounds (p. 8 5 ) and these itre stored initially in nephrocytee
which either rtecurnulatc. in the body or are transported out across the
epithelium. Although Iittlc is know-ii about' the orange cells their
almost universal occurrence in asciditins suggests that they play a
significimt role in metabolism. The pigment is not, as first suggested,
a carotchne but may be iL derivative of melanin or perhaps of vanadium.
Howevw, orange cdls occur in many species in which vanadium does
not occur.
AsciditLn blood tnay t h u s bc coiisitlered to have three functions :
nutrition, storage excretion and test formation.
x. NrTftoUEN EXCRETION
Ascidians (lo riot posmss ibny form of regulatory organ such as H,
kidney or a nephridial system, but in a great many species there tire
structures in which certain types of' metabolic waste may be accumulated in solid form (Fig. 24). In the simplest case, and occurring in
most ascidians, granular concretions are deposited in special blood
cells termed nephrocytes. The concretions are usually considered to be
purine in nst'urc and the nephrocytes either remain in circulation or
are deposited in the tissues perhaps eventually being passed to the
The prwise role of' t h e two types of rcinoehocyte is difficult to define
and there is little in the litcrature to enable firm conclusions to be
reached. I h t h thr hyaline mid the granular amoebocyte are reported
to be phagovytic and tlhe former has considerable powers of amoeboid
movement. Azbma (1!)37) has drawn attention to the fact that the
distinction bctween these two anioebooytcs is not always clear and that
in fact, they may be different stages of a single cell type. The strongly
amoeboid prol)ertirs of thv hyaline type may be associated with
phagocytic activity, while the less mobile mature granular cell may be a
contrasting metabolic phase. In any event it seems likely that both
types are cwiccmied in some way with the basic nutrition and metabolism of the imimal ; modern tmhniques in biochemistry should be able
to throw more light, on this problcm. Kalk (196313) believed that the
hyaline amoeboc*yte phagocytizes beads of vanadium-laden mucus in
the pharynx and gives rise to vacuolar amoebocytes and signet-ring
cells.
Both thc nephrocyte and the orange pigment cell appear to be
depositories for metabolic waste products. The absence of certain
uricolytic enzymes results in incomplete metabolism of purines and
related compounds (p. 8 5 ) and these itre stored initially in nephrocytee
which either rtecurnulatc. in the body or are transported out across the
epithelium. Although Iittlc is know-ii about' the orange cells their
almost universal occurrence in asciditins suggests that they play a
significimt role in metabolism. The pigment is not, as first suggested,
a carotchne but may be iL derivative of melanin or perhaps of vanadium.
Howevw, orange cdls occur in many species in which vanadium does
not occur.
AsciditLn blood tnay t h u s bc coiisitlered to have three functions :
nutrition, storage excretion and test formation.
x. NrTftoUEN EXCRETION
Ascidians (lo riot posmss ibny form of regulatory organ such as H,
kidney or a nephridial system, but in a great many species there tire
structures in which certain types of' metabolic waste may be accumulated in solid form (Fig. 24). In the simplest case, and occurring in
most ascidians, granular concretions are deposited in special blood
cells termed nephrocytes. The concretions are usually considered to be
purine in nst'urc and the nephrocytes either remain in circulation or
are deposited in the tissues perhaps eventually being passed to the