544 ANTHON. [Vora 
which lies in the median dorsal line, extending from the 
second to the extreme segment: The much darker alimen- 
tary canal shows on either side of the heart, while the large 
lobulated caecum extends two-thirds of the way up the left 
side. ‘The superficial tracheal system, which consists of the 
two main lateral trunks with their cross-connections, stands 
out as slender, shining white strands. On the ventral sur- 
face, the ventral ganglia, with their lateral branches, show 
very clearly. It is this readiness with which the main ana- 
tomical features can be made out that renders Ctenophora 
larvee such remarkably fine subjects for students in ento- 
mology. 
The mouthparts are very complex, and their exact homolo- 
gies cannot be accurately determined save by a very extensive 
embryological study. The short single-jointed antennz arise 
from the small lobe of the plate covering the top of the head. 
The antenne bear at their extremity two groups of sensory 
papillae. The mentum is triangular, with three serrations on 
each side and a larger apical tooth. The mandibles (Fig. 8) 
are strong and heavy. On the inner side of each mandible 
there is attached the serrated mandibular lacinia, which is 
evidently of great importance, as it is so very well developed. 
The structure of the maxilla (Fig. 9) is extremely compli- 
cated and no definite homologies can be made out. The 
lacinia, a row of fine projections, lies next the mentum. On 
the outer side a very short palpus shows, and is carried on the 
short, curved palpiger. Back of this extends the head sclerites. 
The entire body of the larva is covered with fine, close- 
set, simple hairs, pointing backwards. These are very much 
thicker on the anterior part of the body, and gradually 
decrease in number toward the posterior. This fact of dis- 
tribution would tend to show that these hairs are somewhat 
sensory in function. Besides these there are larger hairs 
(Fig. 10), collected here and there in groups of from two to 
six and probably sensory in function. These large hairs are 
hollow with a central pore canal and are, in common with the 
shorter Ones, somewhat useful in locomotion. 
