1. Ackerman, G. A., and Knouff, R. A., 1959, Lymphocytopoiesis in the bursa of Farbricius, Am. J. Anat. 104: 163.
2. Bang, F. B., 1967, Defense reactions in invertebrates, Federation Proc. 26: 1713–1715.
3. Beddard, F. E., 1890, Contributions to the anatomy of earthworms, Quart. J. Microscop. Sci, 30: 460.
4. Benham, W. B., 1891, The nephridium of Lumbricus and its blood supply, Quart. J. Microscop. Sci. 32: 293–334.
5. Burnet, F. M., 1968, Evolution of the immune process in vertebrates, Nature, 218: 426–430.