Nofe. 455-456.] 



HEAD OF BLATTA. 



797 



with the first, have become 



The Development of the Head Sceerites. 



As before stated, it is only in the most inridcnlal manner 

 that insect embryolofj^ists have tonched upon the (k'\eloi)nicnl ot 

 the head sclerites. Ik^fore presenting- my ('om lu>ion^ i-onrorn- 

 ingthe development of the head capsule of l^Iatta, 1 shall brielly 

 review the more important of the scattered tctcrrncrs, reM.a \ in.i; 

 comment until we are ready to compare the \ ie\v,s lhu> e\pi e>>eil 

 with the results of my work. 



The earliest of the references was that of Zaddach ('54)- 

 This pioneer worker has not received due credit tor what he so 

 independently accomplished. Many general features of the 

 embryological develo[)ment of insects, though credited to much 

 later writers, were clearly outlined by Zaddach. Working alto- 

 gether with entire mounts, it is but natural that his conclusions 

 regarding the external changes should be the most accurate. It 

 was he who first pointed out the post-oral origin of tlic anlemKc, 

 and called attention to a special antenna! segment distina tn.m 

 the cephalic lobes. He described the procr])halon (" Vonhr- 

 kopf), and derived from it the labruni, tlie clyi)cus and the 

 front hintcn r nnd vordcn r Kopjschild und ( )hi rlippc "). He 

 believed that the cephalic lobes formed the bulk of the head 

 capsule, while the Y-shaped sutiu-e represented the line ot tusKm 

 of the cephalic lobes and the proc-e])]ialon. 



Huxley ('58) gave a more accurate dcMriptmn ot tin- pro 

 cephalon. He also gave a fuller account oi the dorsal flexure ot 

 the cephalic region, as a consequence ot which "the hueot attai 1- 

 ment of the bases of the eyes and antetuia is tre(|uentl\ alto- 

 gether above that of the other ai)])en(lages, so that they appear 

 to be tergal, and not sternal, a])pendages. I he pfocephalu 

 lobes he regarded as the sternite of the first, or oi)thalmic. scg 

 ment and though he does not make a direct statement, the 

 inference is that his antennulary and antennary sterna are 

 represented bv the labrum and the clypeus. 



Packard in his earlier work devoted some attention to the 



