LITERATURE OF THE AMPHINEUVURA 63 
ganglionic swelling. A small perirectal commissure originates 
from this swelling. The pedal cords are united with one another 
and with the pallial cords of the same side by anastomoses in the 
anterior region of the body. A small stomato-gastric commissure, 
bearing two small stomato-gastric ganglia on the middle of its 
course, arises from the cerebral ganglia and surrounds the 
oesophagus. There are no organs of special sense except a dorsal 
posterior and median pit, corresponding to the precloacal fossa of 
the Neomeniomorpha. 
The sexes are separate. The azygos gonad occupies the same 
position as the paired gonads of the Neomeniomorpha, and com- 
municates by a median aperture with the pericardial cavity. The 
generative products are conducted from the pericardium to the 
exterior by the renal ducts. The embryology of the group is quite 
unknown. 
The Chaetodermomorpha are marine animals feeding on lowly- 
organised forms of life, such as Protozoa, ete. They are found im 
oozy bottoms from a depth of 15 fathoms to abyssal regions. 
The nine recorded species of the single genus Chaetoderma come 
from the North Atlantic, North Pacific, and Arctic Oceans, the Sea 
of Marmora, the Eastern Archipelago, and the Philippine Islands. 
Family CHAETODERMATIDAE, von Jhering. Genus—Chaetoderma, 
Loven. The characters are those of the sub-order. Liméifossor, Heath 
(Alaska). 
PHYLOGENY OF THE AMPHINEURA, 
The Polyplacophora present the most archaic characters among 
the Amphineura. The Aplacophora, on the other hand, are 
specialised in the following respects: (1) in the great reduction of 
the foot ; (2) the disappearance of the shell (Cryptoplaz, among the 
Polyplacophora, shows how these two reductions may take place 
simultaneously); (3) the absence of the radula in several forms. 
The Chaetodermomorpha seem to be more specialised in these 
points than the Neomeniomorpha. 
LITERATURE OF THE AMPHINEURA. 
I. Polyplacophora. 
1. van Bemmelen. Zur Anatomie der Chitonen. Zool. Anzeiger, 1883, p. 340. 
. Blumrich. Das Integument der Chitonen. Zeitschr. f. wiss. Zool. lii. 
1891, p. 404. 
3. Burne. Notes on the Anatomy of Hanleya Hanleyi, M. Sars. Proc. 
Malacol. Soe. ii. 1896, p. 4. 
4. Garnault. Sur la structure et le développement de l’euf et de son follicule 
chez les Chitonides. Arch. Zool. Expér. (2), vi. 1888. 
. Haddon. On the Generative and Urinary Ducts in Chitons. Proc. R. 
Dublin Soc. new ser. iv. 1885. 
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