A, The larva of "Echinorhynchus proteus" from the body cavity of "Phoxinus laevis", with the proboscis retracted and the whole still enclosed in a capsule. B, A section through the same; "a," the invaginated proboscis; "b," proboscis sheath; "c," beginning of the neck; "d," lemniscus. Highly magnified (both from Hamann). From "Cambridge Natural History", vol. ii., “Worms, &c.,” by permission of Macmillan & Co., Ltd.