the structure and control of the blood vessels of invertrebrates
Institution: | Boston University |
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Department: | |
Year: | 1940 |
Record ID: | 1485006 |
Full text PDF: | http://hdl.handle.net/2144/4123 |
As a large Metazoa developed, osmosis and streaming of protoplasm had to be replaced by a more efficient maintenance system. A complex arrangement of invaginations would provide sufficient absorptive area, vut no advance is possible with such a system. Circulation is an effective means of distributing materials, but a large body with an entire surface cannot absorb enough material to maintain itself. By combining systems of invaginations and circulation, however, the poor features of each system are eliminated.