Giard A., 1879. Phoronis hippocrepia. Bull. Sci. Dept Nord, 10, p. 24.

Giard A., 1878. Classification du règne animal. Bull. Sci. Dept. Nord, 10, 2-3.

Lankester E. R., 1877. Notes on the embryology and classification of the animal kingdom: comprising a revision of speculations relative to the origin and significance of the germ-layers. Q. J. microsc. Sci., 17, 399-454.

Lankester E. R., 1873. A contribution to the knowledge of haemoglobin. Proc. Roy. Soc. London, 21, 70-81.

Claus C., 1872. Grundzüge der Zoologie, Elwert, Leipzig.

Metschnikoff E., 1871. Über die Metamorphose einiger Seethiere. III. Über Actinotrocha. Z. wiss. Zool., 21, 244-252.