ATLANTIC AND CARIBBEAN PYCNOGONIDA—HEDGPETH 179 
expressions of the dynamics behind the 8-legged species they resemble. 
It cannot be an accident of a mechanistic universe that these 10- 
legged forms occur in groups whose success is already indicated by 
their large contingents of closely related “normal” species. 
Why, then, have I retained artificial species, genera, and families, 
insisting on keeping the Tanystylidae separate from the Ammotheidae, 
and indulging in other inconsistencies? The principal reason, aside 
from the perennial problem of simplifying classification for reference 
purposes after the manner of a library catalog system, is the recogni- 
tion of divergence within the group. The Pycnogonida is a young 
group, albeit an apparently useless one by anyone’s teleology or eco- 
nomic interests, and if the dynamic force that is expressing itself in 
this particular group of organisms continues, the lines of divergence, 
now conceived as arbitrary, may become broader in time and be rec 
ognized as “natural” divisions by the taxonomists of a subsequent 
millennium. 
In the meanwhile, we must proceed with our subjective appraisals 
of species. I regret the necessity for describing species on the basis 
of single specimens, for giving the same name to groups that are alike, 
but yet not quite the same, e. g., the Brazilian and North Atlantic 
forms of Tanystylum orbiculare and the northern and southern forms 
of Nymphon macrum, and other vagaries of my human imperfection, 
splitting or lumping as seems best at the moment. But if we made it 
a hard and fast rule not to describe a species from a single specimen, 
we would have to wait some time for information concerning the 
extent of divergence and variation within the group. Some of these 
creatures dredged from the bottom of the sea may never be found 
again, and statistical or comparative methods require, for perfection, 
more material than is available even in some of the largest series 
before me. And even an amateur does not have all the time he would 
like to have to devote to his studies. Eventually the taxonomists of 
the great museums will devise methods for such organisms as the 
pycnogonids, involving perhaps the use of extensive series of super- 
imposed camera-lucida drawings or photographs, which will clarify 
the status of species in such aggregates as Nymphon. Until that 
happy day, the present methods, as applied in the following pages, 
will have to do.% 
Family NYMPHONIDAE Wilson, 1878 
Ovigers 10-jointed, in both sexes. Chelifores chelate, 2-jointed; 
palpi 5-jointed. With one decapodous genus. 
In agreement with other writers, particularly Calman (1915a) and 
16 Some possible ways of dealing with the taxonomic problems reviewed above are discussed by Isaac 
Ginsburg, in ‘Divergence and Probability in Taxonomy.” Zoologica, vol. 25, No. 1, pp. 15-31, 1940. Other 
references will be found in his paper. This discussion was written before I had read Mayr’s ‘“‘Systematics 
and the Origin of Species.”’ 
