330 REPORT— 1885. 
bably related ancestrally to the larval or adult forms of Phyllopods like 
Apus, Lepidurus, &c. whilst the relationship between the living Nebalia 
and the numerous genera of Palozoic Pod-shrimps does not necessarily — 
preclude us from considering these forms as still belonging to the Enro- 
mosTRACA, although placed in Packard’s order PHYLLOCARIDA. 
As to the question of ornamentation, upon which Herr Dames insists 
so strongly, the concentric striz, marking lines of growth, appear to 
correspond most closely in character and origin with the similar decora- 
tion observable on the valves of Hstheria, Limnadia, &c. so that their 
absence upon the carapaces of Apws and Nebalia does not necessarily 
prove that shields so ornamented cannot be deemed to belong to Crustacea 
or even to the PHy.Lopopa; whilst many of the carapaces of the fossil 
genera, e.g. Dithyrocaris, Ceratiocaris, &c. have either concentric or 
anastomosing striz covering the entire surface of their carapaces ; yet 
Herr Dames has evidently no doubt that these forms are related to Nebalia, 
which has a smooth carapace destitute of ornamentation. 
He reminds us that Claus and Gerstaeker are of opinion that Nebalia 
is not a Phyllopod. Because Nebalia during its embryonal life (whilst 
still in the egg) passes through the ‘ Nauplius-’ and ‘ Zoéa-stages,’ which 
in Decapods occur partly in the free state, it has been regarded by some 
as a ‘ Phyllopodiform-Decapod.’ The potentiality of a form to attain to a 
higher existence seems to be here mistaken for actwality. Since it’never 
attains a higher development as an adult than that of a Phyllopod, and 
has no retrograde metamorphosis, may we not with as equal reason regard 
Nebalia as a highly-organised Phyllopod, as to assert that it is a Decapod 
arrested at the Phyllopod stage ? 
All who have studied the PuyLiopopa have been struck by the peculiar 
points of special interest to be observed in Nebalia.' 
Milne-Edwards, in his ‘ Histoire Naturelle des Crustacés’ (1840), 
places Nebalia in the family Apuside among the Phyllopods; at the same 
time he remarks, ‘The Nebalie are very singular little crustaceans, 
which, by reason of their stalked eyes? and their carapace, approach the 
PopopuHTHALMi4; ,they do not, however, possess branchiw, properly so 
called, but they respire by the aid of their thoracic feet, which are 
developed into membranaceous and foliaceous appendages. They resemble 
in many respects, and establish a passage between Mysis and Apus.’ 
Baird (1850) founded the family Nebaliade, and regarded Nebalia as 
a Phyllopod. 
Prof. J. D. Dana (1853), in his great work on the Crustacea, retained 
the family name (Nebaliadw), which he placed in the PuynLopopa. 
Metschnikoff in 1865 published an abstract of his account of the 
development of Nebalia Geoffroyi, and in 1868 the full essay in the 
Russian language. Fritz Miiller, in his‘ Fiir Darwin,’ states that Metsch- 
nikoff has observed ‘that Nebalia, during its embryonal life, passes 
through the Nauplius- and Zoéa-stages, which in the Decapoda occur 
1 For a very full account of Nebalia see the twelfth Annual Report of the United 
States Geological Survey, Part I. Geology, Paleontology, and Zoology, 8yo, 1883 
(Washington), ‘A Monograph of the Phyllopod Crustacea of North America, with 
remarks on the order Phyllocarida,’ by A. S. Packard, jun., pp. 295-592, and plates 
i-xxxix. See also the American Naturalist for October, November, and December, 
1882, vol. xvi. pp. 785, 861, 945. 
2 Pedunculated eyes are also present in Branchipus and Artemia, so that the 
stalked eyes of Webalia can scarcely be regarded as an essentially distinctive character- 
‘. 
