No. 2.] ANURIDA MARITIMA. 27% 
tive of its future anal position, although at this time the germ 
band is not yet laid down. By a somewhat early migration the 
entoderm cells are scattered, and finally assume their definite 
relations at a very late embryonic period. It is, of course, pos- 
sible that the entoderm cells even at this stage assist in the 
transformation of the yolk, but there are certainly separate yolk 
cells for this duty. . 
As readily seen, the process of entoderm formation in Anu- 
rida agrees very closely with the method found among some of 
the Crustacea. In many members of this group the entoderm is 
early differentiated from the rest of the cells, but remains sta- 
tionary for a long time, simply imbedded in the yolk. In some 
cases its origin is still under discussion; some authors claim 
that it is composed of vitellophag cells that have been function- 
ing in the egg from the beginning; in many cases the entoderm 
only assumes its permanent relations at a late period of devel- 
opment. Zograff (90), describing the origin of the mesenteric 
lining in two species of Geophilus, says that it appears from the 
yolk, and concludes that the process closely resembles that found 
in Malacostraca and Arthrostraca. Heathcote ('s6) describes 
it for Julus terrestris in the following way: Certain cells during 
cleavage remain behind in the yolk and form the entoderm, and 
in turn give rise to the middle germ layer. After the appear- 
ance of the ectodermal parts of the alimentary tract the scat- 
tered entoderm cells arrange themselves to form a central lumen 
and give rise to the mesenteron. From these few points of 
comparison it is clear that Anurida constitutes an interesting 
intermediate form, connecting the processes typical of the 
crustaceans and myriapods with those of the higher Insecta. 
It is difficult to say to which of the lower arthropod groups 
Anurida is the more closely allied, especially as so little work has 
been done on the myriapods. Certainly the resemblances to the 
group last mentioned are very striking. The interpretation of 
the differences found between the higher insects and Anurida 
would point to a gradual delaying of the entoderm formation to 
a later embryonic period in those eggs possessing a larger 
quantity of yolk. This new relation possibly raises again the 
question as to whether all the cells resulting from cleavage of 
