NEMATODA. 
505 
pendent division of the Vermea^ related to the Nematoda, Gepliyrei^ and 
Acanthocephala. 34 species are enumerated : 9 from Europe, 2 from 
Asia, 5 from Africa, 12 from America, and 5 from Oceania ; tlie follow- 
ing described as new: — G. ameus p. 52, pi. ii. fig. 12 (Cumana) ; Icuvis, 
p. 52 (New Caledonia); incertus (Tasmania) and gracilis (TenerifEe), 
p. 53 ; deshayesi (Caraccas), p. 53, pi. i. fig. 3 ; suhareolatus (Is^re, 
Hautes Pyrenees), p. 54, pi. ii. fig. 10 ; chinensis (China), p. 56, pi. ii. 
fig. 7 ; hlanchardi, p. 56, pi. i. fig. 1 (Mauritius) ; ahhreviatiis (I. 
Bourbon), p. 57, pi. i. fig. 4 ; reticulatus (California), p. 57, pi. i. fig. 5 ; 
prismaticus (Bogotd), p. 58, pi. i. fig. 2 ; trilobus (Jersey), p. 59, pi. ii. 
fig. 9 ; caledoniensis (New Caledonia), p. 62, pi. ii. fig. 8 ; tuherculatus 
(Rockhampton), p. 63. The figures cited, and those of G. tolosanus, 
pis. i. fig. 6, ii. fig. 11, give only the areolation, '&c., of the skin, 
which plays a prominent part in the determination of the species. 
[The idea of the author, that species are only subjective concep- 
tions, of which the “ caractdristique ” given is the essential thing, 
would, of course, induce as its consequence, endless changings of 
names, and confusion in nomenclature.] A full account of the anatomy 
of the adult worm (in which the mouth is wanting, and the intestinal 
channel rudimentary) is given ; under the tegument (consisting of a struc- 
tureless cuticule and a fibrous skin) lies a continuous layer of longitu- 
dinal muscles, only divided along the mesial ventral line by a vertical 
band of nervous filaments, which establishes the communication between 
the peripheral nervous layer, interposed between the integument and 
the muscular layer, and the ventral nervous string which is placed be- 
tween the intestine and the muscular layer, and provided at each end of 
the body with a ganglion-like expansion. At the anterior extremity 
the peripheral layer is strongly developed, and forms, reposing imme- 
diately on the ganglion-like termination of the ventral chord, a sort of 
nervous hood, possibly adapted for visual purposes ; the sensorial papillae 
of the skin throughout receive filaments from the multipolar nervous 
cells of the peripheral layer. In the cloaca, terminate the intestine and 
the two large reservoirs for the eggs and sperma, which are placed on 
each side of the obliterated alimentary channel. The eggs arc deposited 
in strings in the water ; their evolution is described in all its prin- 
cipal phases (the embryonal cells are the progeniture of the germinative 
vesicle, the true cell of the egg). The embryo has a wrinkled skin, a head, 
tnouth, proboscis, oesophagus, and intestine, and a secretory apparatus, 
consisting of some gland-cells and a duct opening close to the base of the 
three stylets of the proboscis ; the head is further armed with three circles 
of spines, forming a rather complicated piercing apparatus ; the body-cavity 
is filled up with embryonal cells, from which the muscles, nervous sys- 
tem, and, at a much later period, the sexual products, are developed 
in succession. By means of the stylets, &c., the larvae penetrate the ^ 
aquatic larvae of Diptera (Chironomus), in which they encyst, though pre- 
serving a certain freedom ; when the dipterous larvae are devoured by 
fishes {Phoxinif Cobitis), they are set free again for a short time, but 
soon establish themselves in the walls of the intestine, where they may 
be found quiescent and encysted in autumn in great numbers ; the dif- 
