522 PYCNOGONIDA " CHAP. 
majority of cases studied the larval Pycnogon is at first provided 
with three pairs only, the three anterior pairs of the typical 
adult. Numerical coincidence, and that alone, has often led this 
“Protonymphon” larva to be compared with the Crustacean 
Nauplius. In the annexed figure of a young larval Ammothea 
(Achelia), we see the unsegmented body, the already chelate 
chelophores (furnished with 
the provisional cement-glands 
already described), the other 
two pairs of appendages each 
with a curious spine at its 
base, the gut beginning to 
send out diverticula (of which 
the first pair approach the 
chelophores) but still desti- 
tute of the anus (which is 
only to be formed after the 
development of the abdomen), 
the proboscis, and one pair of 
eyes situated close over the 
pre-oral ganglia. The subse- 
quent changes are in this 
genus extremely protracted, 
Fic. 280.—Young larva (nat. size "1 mm.) of gnd terminate with the loss 
Ammothea fibulifera, Dohrn. C.G', Brain ; : . 
gl, gd, gland and duct of chelophore ; of the chelae, a& process which 
pr, proboscis ; I, Il, II, IV, appendages. gecurs so late in life that the 
(After Dohrn.) ewe 
chelate individuals were long 
looked upon as belonging to a separate genus, the original 
Ammothea of Hodge, until Hoek proved their identity with 
the clawless Achelia. 
The developmental history of Phoxichilidium and Anoplo- 
dactylus is peculiar. The young larvae have the claws of the 
second and third appendages hypertrophied to form enormous stiff 
tendril-like organs, with which they affix themselves to the bodies 
of Hydroid Zoophytes (Coryne, Eudendrium, Tubularia, Hydrac- 
' The correspondence is not universally admitted. Meinert (Ingolf Expedition, 
1899) believes that the second and third appendages of the larva disappear, and 
that the palps and ovigerous legs are new developments ; so giving to the normal 
Pycnogon nine instead of seven appendages. See also Carpenter ‘‘On the Relation- 
ship between the Classes of the Arthropoda,” Proc. R. Irish Acad, xxiv., 1903, 
pp. 320-360. The latest observer (Loman) inclines to the older view. 
