604. ALLIS. [Vov. XII. 
branch arising some little distance beyond the most distal 
one of the group. There must accordingly have been fifteen 
organs or groups of organs in the infraorbital canal on the left 
side of the head, and either fifteen organs or fourteen organs, 
one of them double, on the right. Unfortunately no attention 
had been given at the beginning of the dissection, which was 
begun on the left side, to determine, either the number of den- 
dritic systems or the number of sense organs in the canals, 
it being assumed, from earlier embryological work, that the 
branches of the nerves concerned would everywhere fully 
indicate the number of sense organs and the arrangement 
of the dendritic systems. After the dissection of the left side 
had been nearly completed and fifteen branches of the buccal 
instead of fourteen had been found, the advantage of knowing 
the number and position of the sense organs in the different 
canals became apparent, and on the right side the outer sur- 
face of all the bones concerned was carefully removed, so as to 
lay open the canals that traversed them and thus expose, zx 
situ, the sense organs, and the ends of the nerves that supplied 
them. The number and position of the organs, as indicated by 
the projecting nerve ends, being everywhere normal on this 
side, no further thought or attention was given to the matter. 
Later it was found that one of the branches of the buccalis was 
double at the end, but as the dermal bones had all been removed 
it was too late to determine which organ or organs had been 
supplied by it. In my earlier work on larvae, groups 11 and 
12 infraorbital were always supplied, either by branches of a 
single nerve or by nerves arising close together from the buc- 
calis, and there should therefore normally be, both in the adult 
and in the embryo, but ten groups of organs beyond group I1, 
and but ten nerves beyond the double nerve supplying groups 
It and 12. In the present instance, in this specimen used for 
illustration, there were, however, eleven such nerves on each 
side of the head. There must, therefore, have been an extra 
system, 10’, on both sides, or, assuming no error in observation, 
the nerve to group 11 must have become somewhat widely sep- 
arated at its origin from the nerve to group 12, and that group 
must have become entirely double on the left side, and partly 
