456 
FLORENCE BUCHANAN. 
time at which the gill is developed, and to the condition of the 
appendage at that time, I think we can account for all the 
different positions of branchiae in the higher Crustaceans. 
In some of the Euphausidae the branchiae of the hinder 
thoracic appendages may be highly complex, the second branch 
developing other branches on it, but only in Nematoscelis are 
these branches apart from each other. In all they are unpro- 
tected, and not covered by the carapace, the secondary 
branch usually reaching over on to the ventral surface of the 
animal. 
All the Euphausidae undergo a free metamorphosis, hatching 
in the Nauplius condition, and passing through a number of 
stages, varying from four to eight, before reaching their adult 
and permanent form. The first traces of gills appear in all 
cases to arise soon after, and in some cases even before, the 
development of the limb to which they are finally attached. 
This is all that Sars (who gives a nearly full account of the 
development of the Euphausidae found in the “ Challenger” 
expedition) states about the development of the gills. Their 
appearance before the leg to which they are attached seems 
to point to the existence at an earlier period of an epipodite 
which was used in swimming, and which has now disap- 
peared. In all the Euphausidae the endopodite develops 
before the exopodite, as is not the case with the higher 
Crustaceans. 
The structure of the gill of the Euphausidae (figs. 3, 4), 
is very simple, consisting merely of branching lobes with no 
secondary branches. 
In the Lophogastridae, which are also Schizopods, but of 
a higher order than the Euphausidae, the primary lobes of the 
stem are themselves lobed, and thus the gill is more complex 
in structure (fig. 5). The final ramifications may be either 
foliaceous, as in Lophogaster itself, or vesicular as in Gnatho- 
phausia (Sars). The arrangement of the gills is also different : 
instead of being attached to the limb itself, each complex gill 
is attached to the arthrodial membrane near the base of the 
appendage, as first stated by Boas and afterwards confirmed by 
