98 ZOOLOGY. 
layer of cells, nor of any organs, all the animal and vegeta. 
tive functions being accomplished by the activity of the 
ectodermic cells and of the single axial cell. There is no 
mesodermic cell or cells. On account of these characteris- 
tics, Van Beneden 
regards these or- 
ganisms as forming 
the type of a new 
branch of the ani- 
mal kingdom, 
which he distin- 
guishes as Mesozoa. 
He places the 
branch, or sub- 
kingdom, between 
the Protozoa and 
all the many-celled 
animals (Metazoa), 
%, and includes the 
ON hypothetical Gas- 
Y treades of Haeckel 
in the branch. 
Sy Geoh 4 )s While this position 
2) es ok j2§ may prove to be 
y “iN Wk A'& the correct one, we 
W) Clo) X 4.\\\ _ should prefer, while 
eXgg) CW *ealQy not overlooking the 
a, \4) resemblance of the 
Dicyemide to the 
Infusoria, and even 
Fig. 62.—a, Dicyemella Wagneri ; 9, 9, germigenes; n, : 
eles of the axial cell ; 5, the ep’ ereal went ot Dicye- the Gregarinz to 
mella, with its striated nucleus ; c, the same beginning a 2 
to undergo self-division ; d, final stages of self-division wait for more light 
(morula); e and /, infusoriform embryo; A, germs of 
the vermiform embryos of Dicyema typus; i, gastrula On the development 
of the same; &, J, m, 0, different stages of vermiform a 
larvae of Dicyema typus, all highly magnified.—After E, Of the parasitic 
icc Platyhelminth 
worms. It is not improbable, on the one hand, that the 
Dicyemide, retaining their parasitic life, are retrograde 
forms, which have originated from some low Cestoid or 
Trematode worm, and bear the same relation to them, the 
