'I'he mihi11 circulatrion through tho body does not exhibit any unusual
features and there is a through circulation in which the blood completes
a single circwit in about one minute in Ciona intestinah (Skramlik,
1929). The unusual fcature of the system is the additional circulation
provided for the test and it is probably to this circulation that we
should look for u solution to the problem of heart reversal. In many
ascidians thc ciroulation in the test is of great importance as growth and
maintenance of the structure is carried out by blood cells. The nature
of the circdution varies from genris to genus and in Ciona is restricted
to the postcrior peduncle. In many other genera (e.g. Ascidia and
Corella) there are several main chsnnthls running through the test and
arising from these are periphwctl channels which run toward the surface
where they end in ampullary swolling,s. The main channels are divided
by a mesenchymstous septum and the two halves connect to opposite
ends of the heart, hit many of the peripherd vessels have no septum
and " two way " circulatiori in them is impossible. During normal
activity of tlio lieart the blood in such peripheral vessels oscillates to and
fro with each pulsution of the heart but at the moment of heart beat
reversal when blood pressurc momenturily drops blood tends to drain
out of those vcwels into the intiin c*hannels and thus effect a renewal of
blood. This suggests that some form of' elastic recoil must take place in
the anipullue and peripheral vessels to help force blood into the main
circulation. These observations only suggest the sort of functional
problem which may be associated with heart reversal and considerable
biophysical research needs t o be done to determine the forces involved
and whether any oonnwtion between the two exists.
IX. ASCIUIAN BLOOIJ
Ascitliun t)lood is characterized by three 11 nusual feat'ures.
(a) The plusma, while igotonic with SPU watvr, has low concentrations
(b) There are at least eight different type5 of blood cell.
(c) Certain blood cells contain organo-met :d compounds incorporating either venadiuni or iron, and these cells trequently, if not always,
contuin high cmncentrations of sulphuric acid.
Earlier reviews 011 the blood are to be Sound in George (1939),
Webb (1939, 1956), Pdrbs ( I 943) and Eliassen (1954).
of sulphate t~nd of carbon dioxide.
A. The plnsma
henze (191 I , 1912) was the first worker to ;malyse the plasma of an
ascidian (Phailusin mamtnillata) and his findings have been confirmed by
features and there is a through circulation in which the blood completes
a single circwit in about one minute in Ciona intestinah (Skramlik,
1929). The unusual fcature of the system is the additional circulation
provided for the test and it is probably to this circulation that we
should look for u solution to the problem of heart reversal. In many
ascidians thc ciroulation in the test is of great importance as growth and
maintenance of the structure is carried out by blood cells. The nature
of the circdution varies from genris to genus and in Ciona is restricted
to the postcrior peduncle. In many other genera (e.g. Ascidia and
Corella) there are several main chsnnthls running through the test and
arising from these are periphwctl channels which run toward the surface
where they end in ampullary swolling,s. The main channels are divided
by a mesenchymstous septum and the two halves connect to opposite
ends of the heart, hit many of the peripherd vessels have no septum
and " two way " circulatiori in them is impossible. During normal
activity of tlio lieart the blood in such peripheral vessels oscillates to and
fro with each pulsution of the heart but at the moment of heart beat
reversal when blood pressurc momenturily drops blood tends to drain
out of those vcwels into the intiin c*hannels and thus effect a renewal of
blood. This suggests that some form of' elastic recoil must take place in
the anipullue and peripheral vessels to help force blood into the main
circulation. These observations only suggest the sort of functional
problem which may be associated with heart reversal and considerable
biophysical research needs t o be done to determine the forces involved
and whether any oonnwtion between the two exists.
IX. ASCIUIAN BLOOIJ
Ascitliun t)lood is characterized by three 11 nusual feat'ures.
(a) The plusma, while igotonic with SPU watvr, has low concentrations
(b) There are at least eight different type5 of blood cell.
(c) Certain blood cells contain organo-met :d compounds incorporating either venadiuni or iron, and these cells trequently, if not always,
contuin high cmncentrations of sulphuric acid.
Earlier reviews 011 the blood are to be Sound in George (1939),
Webb (1939, 1956), Pdrbs ( I 943) and Eliassen (1954).
of sulphate t~nd of carbon dioxide.
A. The plnsma
henze (191 I , 1912) was the first worker to ;malyse the plasma of an
ascidian (Phailusin mamtnillata) and his findings have been confirmed by