552 GEOFFREY SMITH. 
The position of the Hoplocarida (Squillidz) as an early 
offshoot from the Decapodan stem must remain at present 
doubtful, but many of their characters point to this conclusion. 
The spherical spermatozoa, the ramified hepatic ceca, the 
complicated metamorphosis, the absence of a lacinia mobilis, 
the presence of an appendix interna on the pleopods, all 
suggest that the Hoplocarida have travelled some way in the 
Eucaridan direction since their derivation from the common 
Eumalacostracan ancestor. That this Eumalacostracan an- 
cestor which diverged from the Leptostracan stock was not 
identical with the Syncarida must probably be conceded. 
But we may perhaps conceive of it as a straight-bodied 
ambulatory Crustacean without a carapace and with all the 
thoracic segments free and uncoalesced, with a tail-fan and 
with all its thoracic and abdominal appendages biramous. 
The thoracic limbs consisted of eight joints, three of these 
joints being distal to the “knee.” It possessed stalked eyes, 
an antennal scale, and two flagella on the antennules, and it 
possibly lacked an otocyst on the antennules. Internally the 
heart was elongated, the alimentary canal had, perhaps, only 
an anterior dorsal diverticulum, and the liver-tubes were few 
and simple. The spermatheca were filiform and there was 
present both an antennary and maxillary gland. It probably 
had a brood-pouch as in the Phyllocarida. 
From this type it was but a step to the Syncarida. Directly 
from this ancestral type sprang the Peracarida, with their 
characteristic brood-pouch ; a certain amount of fusion of 
segments either with the head or with one another took place, 
and certain of them developed, independently of the Eucarida, 
a carapace. 
The Eucarida were probably derived from an ancestor 
which had travelled some way in the Syncaridan direction, 
that is to say, it had an otocyst on the antennules, it had lost 
the brood-pouch, and it had developed certain other characters, 
such as the spermatheca and copulatory styles and a more 
complicated liver and alimentary canal. As it diverged 
from the primitive Syncarida it acquired a carapace, spherical 
