458 
FLORENCE BUCHANAN. 
senting the bract than the flabellum of Apus. The develop- 
ment of the gill may have led to the suppression of the 
epipodite when this first lost its primary significance, without, 
however, representing it either in function or structure 
but in position only. The absence of the epipodite in the 
Euphausidse, therefore, seems to show that, on account of its 
loss of function, it has tended almost entirely to disappear. 
In the Lophogastridse the epipodite, on all the hinder thoracic 
limbs (vii — xm), is either absent or rudimentary, being, when 
rudimentary, a projection quite independent of the gill and 
attached to the basal joint of the limb (fig. 5). On the maxil- 
lipede, however (vi), in all the Lophogastridse, the epipodite is 
well developed, and on this appendage there is no gill to cause 
its suppression. It has been retained, probably, because it has 
acquired a new function, namely, that of producing movement 
of the water in the branchial cavity into which it projects, and 
thus keeping the gills well supplied with oxygen. This lanceo- 
late epipodite, with the same function, is also present in the 
third group of the Schizopods, the Mysidse — where, how- 
ever, there are no gills. According to Professor Claus, the 
Mysidse probably once had gills and were much larger animals 
than they now are. (They are now usually only one third or 
sometimes two thirds of an inch in length.) On account of 
this reduction in size the gills have been lost, and some forms 
have acquired peculiar foldings of the integument round the 
bases of the thoracic limbs, which probably have branchial 
functions. These are covered by the carapace, underneath 
which the water is kept in continual motion by the long 
epipodite of the sixth appendage. The other thoracic append- 
ages, besides having no gill, also have no epipodite. The 
presence of the epipodite of the sixth appendage, in both 
Mysidse and Lophogastridse, and of the rudimentary epipodite 
in some of the Lophogastridse, seems to show that they 
sprung from the Euphausia-stem before the epipodites were 
entirely lost. 
The next group that we come to, the De capo da, of which 
the Crayfish and Crab are well-known examples, originated 
