THE EMBRYOLOGY OF THE HONEY BEE 109 



straight line drawn between them would intersect the germ band 

 behind the mouth, yet their obvious connection with the deuto- 

 cerebral lobes precludes their being seriously considered as any- 

 thing but pre-oral in their relations in this insect. To this segment 

 belong also well developed coelomic sacs, as will appear later. 



The tritocerebral (second antennal, intercalary or premandibu- 

 lar) segment (sBr) is, in the honey bee, of more than ordinary 

 interest, birt since Biitschli (1870) in the embryo of this insect 

 first called attention to the presence of appendage-like swellings 

 in front of the mandibles, between these and the antennae, thus 

 occupying the region afterwards identified as that of the trito- 

 cerebral segment. "Close in front of the anterior angles of the, 

 cephalic plates, between the mandibles and those angles, there 

 arises a conical projection, springing from each of the germinal 

 ridges, which attains a considerable degree of development and, 

 appears almost like a pair of inner antennae" (p. 538). Grassi 

 (1884) also observed these appendages, considering them as 

 the first pair of mouth parts. In another place (p. 201) he 

 states "The first pair of mouth parts, which has an ephemeral 

 existence, may possibly be compared to one pair of the 

 antennae of the arthropods." Tichomiroff (1882) also noticed 

 a pair of transitory swellings in front of the rudiments of the 

 mandibles of the embryo of the silk worm. Wheeler (1893) de- 

 scribed unmistakable vestigial appendages on the tritocerebral seg- 

 ment of the collembolan Anurida. Heymons (1895), although 

 expressing his disbelief in the presence of appendages on this 

 segment in pterygote insects, recognized its presence in the Derm- 

 aptera and Orthoptera and found that it was provided with rudi- 

 mentary coelomic sacs in these orders. Later researches (Uzel 

 1897, Claypole 1898, Folsom 1900), have shown that true append- 

 ages appear on the tritocerebral segment in several apterygote 

 insects, and Uzel has found that in certain forms these appendages 

 may even persist in the imago. Moreover Riley (1904) has de- 

 scribed traces of appendages on the tritocerebral segment in the 

 cockroach. In the honey bee the swellings on the tritocerebral 

 segment first appear at Stage VIII, and attain their greatest 

 development at the stage next following, Stage IX. During these 

 stages they form conspicuous low conical swellings situated a 

 trifle nearer the mid-line than the rudiments of the mouth parts, 



