184 



THE COCKROACH : 



Indications of the appendages appear very early. They give 

 rise to an unpaired labrum, paired antennoc, mandibles, and 

 maxilla) (two pairs). The first and second pair of maxillae have 

 originally, according to Patten,* two and three branches res- 

 pectively. Behind the mouth-parts are found three rudimentary 

 legs. Upon all the abdominal segments, according to Patten, 

 rudimentary limbs are formed ; but these soon disappear, except 

 one pair, which persists for a time in the form of a knobbed stalk ; 



Fig. 105. Ventral Plate of B. germanica, side view. X 20. 



subsequently this, too, completely disappears. Three or four of 

 the hindmost segments curve under the ventral surface of the 

 embryo, and apparently (?) give rise to the modified segments 

 and appendages of the extremity of the abdomen (fig. 105). The 

 ventral plate lies at first directly beneath the egg membrane 

 (chorion), but afterwards becomes sunk in the yolk, so that a 



Fig. 106. Diagram to illustrate the formations of the Embi-yonic Membranes. 

 A, amnion ; S, serous envelope ; B, blastoderm. 



portion of the yolk makes its way between the ventral plate 

 and the chorion. Whilst this portion of the yolk is perfectly 

 homogeneous, the remainder, placed internally to it, becomes 

 coarsely granular, and encloses many roundish cavities and 

 * Q. J. Micr. Sci., Vol. XXIV., page 596 (1884). 



