ON 'THE ANASPIDACEA, LIVING AND FOSSIL. 293 
in place of filiform spermatozoa anda short triangular heart ; 
it specialised an antennary gland and it possessed a compli- 
cated metamorphosis. After its divergence it threw off the 
Hoplocarida and the Euphausiacea. 
If this phylogenetic scheme for the Humalacostraca be 
accepted it is clear that we can no longer look upon the old 
order ‘‘ Schizopoda ” as a natural assemblage standing at the 
base of the Humalacostracan stock. This classification rests 
solely on the biramous structure of the thoracic limbs, and 
ignores all the other organs, whether external or internal, in 
which the various divisions differ so fundamentally. 
We must remain in some doubt as to the presence or 
absence of certain characters in the ancestral Eumalacos- 
tracan which gave rise to the Syncarida, Eucarida and Pera- 
carida. With regard to the brood-pouch it may well be that 
this has been independently acquired by the Leptostraca and 
the Peracarida, and that its absence in the Syncarida repre- 
sents a primitive condition. Again, the otocyst on the 
antennules may have been possessed by the ancestral 
Humalacostracan and lost by the Peracarida. In this connec- 
tion we may mention the striking observation of Professor 
Fritsch, according to which an otocyst was present on the 
inner ramus of the uropods in the fossil Syncarida, Gaso- 
caris and Gampsonyx. If an otocyst was really present 
in this position in these forms we can only suppose that the 
primitive Humalacostracan possessed it, and that it has been 
retained by only a few Peracarida (Mysidacea), and entirely 
lost by the higher Syncarida and Peracarida and by the entire 
division of the Eucarida. 
The reconstruction of the phylogeny of the Malacostraca, 
therefore, leads to the reflection that the primitive ancestors 
of the specialised groups are not distinguished from their 
modern representatives so much by simplicity of structure, 
but rather by combining in themselves the heterogeneous 
elements which have been segregated out in the course of 
evolution and separated into the different streams of descent 
that have given rise to the modern groups. It was the habit 
