DEVELOPMENT OF PHRYGANIDS. 561 



whole length of the original germinal bands. In some cases 

 the rupture is continuous along a transverse line in the head 

 region, and thus a'kind of frontal lappet of the " Hautblatt " 

 is left on that portion of the yolk which limits, the anterior end 

 of the head. This lappet encloses the so-called head cavity which 

 lies between the procephalic lobes ; when, however, in such 

 cases the posterior end of the embryo has grown long enough 

 to reach the head, it fuses with this lappet and thus obliterates 

 the difference between this and the more normally produced 

 condition. 



The appendages are evidently developed from the germinal 

 ridges, and push the edges of the ruptured " Hautblatt " away 

 from the middle line, which now exhibits renewed activity along 

 its lateral margin where it remains continuous with the 

 " Muskelblatt." This activity is manifest in a thickening of 

 the '^ Hautblatt," due to rapid cell-formation which progresses 

 from the lateral to the median edges, and also in the upward 

 growth of this layer which thus envelops the yolk. 



The mandibles first arise and then appear simultaneously 

 behind them the five following segments. Although the 

 antennae appear to develop from the procephalic lobes they are 

 believed to arise from a distinct segment of their own in front 

 of the mandibles, and to correspond to the second pair of 

 antennse in Crustacea, whereas the antennae of the adult insect 

 are claimed to be homologous with the first pair of Crustacean 

 antennse. 



The primitive germ band includes hardly more than the 

 future head and thorax. It increases in length by means of new 

 cell formations, which result in the production of an abdomen 

 by the elongation of which the end of the tail comes to lie 

 next to the mandibles. The abdomen consists of ten segments. 



The author concludes from the way in which the anal stylets 

 are developed that they are true appendages. 



The third period extends from the time of revolution until 

 that of hatching. Four important changes occur in this stage. 

 1. The conversion of the loose cells into a compact granular 

 tissue from which are formed the diflTerent organs. 2. The 



