Nos. 455-456.] 



HEAD OF BLATTA 



An intercstin<^ fact is that, as pointed 011 

 the cephalic lobes arise from three pairs o 

 liferation, which very early fuse. Wheeler 

 centers entered into the formation of the 

 The presence of the three pairs would pre 

 idea that these centers represent future ; 

 thought it might seem that their pn-scnie 

 as to the compound nature of the pieouil n 

 however, that there are three segments 1 

 cephalic lobes, and that these do not fuse 

 the later stages are invaginated with the st 

 dent that the formative centers of tht 

 support to that view. It has been ^u,i;-e 

 represent the three segments whose L,.ni.:^ 

 mation of the brain. That this is not ti- 

 the fact that these areas precede llie deti 

 germ band, and that their fusion and co 

 has taken place long before the deuto- . 

 ments have united with the protocerebral s 



It is during the seventh day. after tl 

 blastopore thickening of the caudal end. tb 

 becomes prominent a pair of thickenm,L;s 

 placed at the cephalic end of the genn \)^ 

 I, c. /.). These thickenings rei.resent the 

 lobes, which are destined to a ni<»st in 

 role in the formation of the head ta])sul.', 

 the first they are connected with thi ,1,^ ■ 

 Of an independent development, siu \\ a- ( ■ 

 by Will ('88) for Ai)his ami by Hu.Km ( 

 Hydrophilus, I find no induation m Hlatta. 



During the eighth day ot enibi\<mu 

 most striking^ change is^^the appc-ai.ui. e a 



Wheeler. The cej^hahc lobes develop la] 

 fu-sl halt (if the ninth day the} 



