62 ANTS. 



large elliptical cells situated in the hypodermis. These cells form a 

 compact mass, formerly supposed to be a ganglion, hut now interpreted 

 as a cluster of unicellular glands that secrete a liquid through the 

 thin chitinous cap of the organ onto the surface of the antenme. It 

 is, indeed, difficult to conceive such sensilhe as having an olfactory 



o . 



function unless their exposed surfaces are moist like- the olfactory 

 organs in the mucous membranes of vertebrates. The nerve termina- 

 tion to the basiconic sensillae applies itself to the cluster of gland cells 

 and then breaks up into delicate branches that pass around and between 

 the latter and up into the conical portion of the organ. 



(b) Clubs Lying in Elliptical Pits ( coeloconic sensillae of Berle-ci. 

 -These may be derived from the preceding type by supposing that the 

 conical hair has come to lie horizontally and to be enclosed in an elon- 

 gated cavity in the chitinous integument (Fig. 32, c). The cellular 

 structure of the organ is essentially the same as that of the basiconic 

 sensillae. 



(c } Champagne-cork Organs of Ford ( ampullaceous sensilhe of 

 Berlese). These evidently represent a further modification of the 

 coeloconic type, on the supposition that the hair becomes smaller and 

 more erect and the pit in which it is enclosed becomes circular, much 

 deeper and opens on the surface of the body by means of a small pore 

 (Fig. 32, </). 



(d) Flask-sliapcd Organs of Lubbock and Ford. Hicks (1859) 

 was the first to describe these extraordinary organs in Mynnica, but 

 Forel and Kraepelin have given a more detailed account of their struc- 

 ture. They are really an extreme form of the ampullaceous sensilla, 

 and may be derived from this by supposing that the chitinous ampulla 

 has become enormously lengthened and attenuated till it forms a narrow 

 sac enclosing the conical hair and connected with the pore in the integu- 

 ment by means of a slender tube running more or less parallel with the 

 surface of the antenna (Fig. 32, g, h}. That these sensillae have devel- 

 oped from those of the preceding type (c~) is shown by the existence 

 of transitional forms both in ants and in other Hymenoptera. The 

 cellular portions of all these forms of ampullaceous sensillae are es>en- 

 tially the same as those of types a and b. 



The gustatory sensillae, situated on the mouth-parts and including 

 those in the terminal joints of the palpi, though resembling the anten- 

 nary sensillae, in general reproduce only the more primitive of the 

 above-mentioned types, that is, those most like the typical tactile and 

 basiconic sensillae. The more specialized ampullaceous types are found 

 only in the antennae. 



The Chordotonal Organs. "Recent studies have shown that these 



