440 GEOLOGICAL SURVEY OF THE TERRITORIES. 
coecal tubes, the series of four lower ones being the four posterior tubes 
described by Claus as passing back into the abdomen. In this section 
the dorsal muscles (dm) of the 
posterior part of the body ap- 
pear, and the ventral muscles 
(wm) are larger than in section 
9, while the ovarian tubes (ov) 
are smaller. 
Without translating in full 
Claus’ description of the heart 
and circulation we will only give 
his conclusions. The heart of 
Nebalia is a long straight tube a 
e little thicker just in front of the 
middle, beginning over the max- 
illa just in front of the 1st 
thoracic segment (tergite) and 
extending to the middle of the 
4th abdominal segment. It has 
two pairs of lateral large ostia 
for the entrance of the venous 
blood, and four pairs of dorsal 
arterial openings in the anterior 
part of the heart. Says Claus: 
“The heart combines the char- 
acters of Phyllopods and Mala- 
Fic. 67.—Section through the end of thorax of Nebalia costraca, while the tubular dor- 
Piper, showing the eh< ace (or), the heart (W), te sal vessel passing through twelve 
cles; vm, ventral muscles ; ne, nervous cord ; ov, ovary ; segments, in its form and in the 
i, intestine. Author del. greater number of ostia resem- 
bles the many-chambered dorsal vessel of the Phyllopods, so on the 
other hand the relation of the two ends with the head and abdominal 
aorte, together with the hinder pair of arteries, reminds us of the swift, 
regular, and in general complicated and vascular circulation of the Mal- 
acostraca. Of especial interest is the similarity of the shell, or cara- 
pace-circulation of the Stomapods and Mysidz with Nebalia.” 
Of especial interest, says Claus, is the sexual apparatus, which com- 
bines in a surprising way in structure and form the peculiarities of 
Phyllopods and Malacostraca (Amphipoda), and also in position and 
topography retains the primitive relation of the ovaries and testes. 
Both are slender, long tubes, which lie right and left on the dorsal side 
of the intestine from the sixth abdominal segment to the region of the 
stomach (kaumagen), and by means of a short cross passage open out 
on the thorax. In the male sex this efferent duct opens in the basal 
segment of the 8th pair of thoracic limbs, namely, in the same place as 
in the Malacostraca. 
Claus includes Nebalia among the Malacostraca, but when we con- 
sider the composite nature of the internal organs as described by him, 
we wonder that he failed to appreciate the independent, synthetic nature 
of the Phyllocaridan type, which, when we take into account the ex- 
ternal as well as internal organization, forbids our regarding Nebalia as 
a true Malacostracan, though the type of a group standing outside of, 
but nearer to the Malacostraca than are the Phyllopods. 
The development of Nebalia.—Our knowledge of the development of 
-Nebalia is due to the distinguished Russian embryologist, who in 1868 
published an elaborate account of the developmental history of Nebalia 
