2i6 THE EMBRYOLOGY OF THE HONEY BEE 



The remaining cells of the visceral wall of the mesoderm mesiad 

 of the genital ridge constitute a loose mesenchymatous tissue the 

 greater part of which is transformed into fat cells. At an early 

 period — Stage XI (Fig. 86B) — a few of the dorsalmost cells of 

 this mass group themselves about the genital ridge, pushing up 

 on both sides of it, and become applied to its outer surface pre- 

 paratory to forming the epithelial envelope of the ovary (Fig. 

 86C and D). 



At Stage X, the genital ridge, as has been said, extends from 

 trunk segments five to ten inclusive. At about Stage XII it loses 

 its connection with the cardioblasts and the splanchnopleure and 

 during the succeeding stages it becomes gradually shorter and 

 thicker (compare Fig. 86B, C and D), until at Stage XIV it 

 extends only from near the anterior end of the seventh trunk 

 segment into the anterior end of the ninth, which is its position at 

 hatching (Fig. XV). Meanwhile the mesoderm cells grouped 

 about the ovarian rudiments have gradually assumed the flattened 

 form characteristic of epithelial cells and are plainly seen to be 

 forming an envelope for the ovaries (Fig. 86, C-D). The attach- 

 ment of this envelope to the heart takes place during Stage XIV. 



The development of the genital organs of the honey bee was 

 first studied by Biitschli (1870), but owing to imperfect technique, 

 his observations are of little value, since he succeeded only in 

 seeing and identifying the ovaries in a late embryo — about Stage 

 XIII. The account of Grassi (1884), although brief, is more 

 satisfactory. This investigator describes and figures the develop- 

 ment of the ovaries, with the aid of sections, and finds that these 

 organs are derived from the mesoderm. He seems however to 

 have failed to observe their origin from the inner (visceral) wall 

 of the mesodermal tubes. Moreover his statement that the genital 

 organs extend almost from the fourth to the eighth abdominal 

 segments is an evident error since at the stage in question (X or 

 XI) they extend much further cephalad. Moreover, the epithelial 

 covering of the genital organs was missed entirely. Petrunke- 

 witsch has more recently (1901, 1902) devoted two papers to an 

 account of the development of the sex organs of the honey bee. 

 In these papers he describes conditions which are to say the least, 

 somewhat peculiar and much at variance with the accounts given 



