186 N. E. McINDOO 
the only olfactory pores on the antenna of the honey-bee. The 
external and internal structure (fig. 8) are like those already 
described by the writer (14 a). 
b. Structure of pore plates. The pore plates or sensilla placodea, 
according to the writer’s discussion of the antennal organs (’14 b), 
were first studied in 1847 by Erichson, who called them olfactory 
organs. Since this date they have been studied by about three 
dozen other investigators whose views concerning their function 
differ widely. In 1851 Vogt suggested that they perform a func- 
tion combining those of smell and touch. In 1858 Lespés com- 
pared them to the ears of higher animals, and a year later Hicks 
called them auditory organs. Practically all of the other authors 
up to 1888, who have studied the pore plates, regard them as 
olfactory organs. Ruland (’88), after having boiled antennae in 
caustic potash, saw that a pore plate is suspended on a membrane, 
resembling a double hinge, similar to that observed in sections 
stained in eosin by the present writer. Owing to this arrange- 
ment, he called them auditory organs. In 1894 Nagel favored 
the olfactory view, but also thought that the pore plates might 
have a mechanical function. He suggested that air pressure 
might affect them. Nine years later Schenk (’03) stated that the 
thick plates in these organs eliminated the possibility of these 
structures being olfactory organs, but judging from their anatomy 
he regarded them as having a mechanical function. He favors 
the view that they are pressure points to inform the bee of the 
object immediately in front of it. 
According to Schenk’s calculations, a male honey-bee has 
31,356 pore plates and a female has only 3,648. According to 
the calculations of the present writer, a drone on an average has 
29,718 pore plates; a worker has 4,744, and a queen has 2,776. 
Those of the drone are much smaller than those of the worker 
or queen, but supposing that their sensitiveness is in direct pro- 
portion to the total area of all their plates, then if the sensitive- 
ness of those on a worker equals 1, that of those on a drone equals 
3, and that of those on a queen equals only 0.6. These organs 
(fig. 3, P) are found only on the fifth to twelfth antennal segments 
of the worker and queen, and on the fifth to thirteenth segments 
