Packard.] 



368 



[January 22, 



5 6 



t 213 



Tlio ombrj'o still farther advanced. 

 r, ganglia. 



iination of the second ^lair of maxillEB, wliicli, united, form the labium, 

 the extremities of which are now situated in the middle of the body. 



The antennae now extend to the 

 middle of the labium, passing just 

 beyond the extremities of the man- 

 dibles and maxillffi. The suture 

 separating the eye - bearing piece 

 from the antennary, mandibular, and 

 maxillary pleurites and supra-clypeus, 

 is distinct; the clypeus is now very 

 distinct, and as large, seen later- 

 ally, as the supra-clypeus, though 

 differing from it essentially in form. 

 The cBsophagus can now be seen go- 

 ing from the mouth-opening and sit- 

 uated just beneath the labium. It 

 curves around just behind the eyes. There ai-e at this period no 

 appearances of movable blood-discs or of a dorsal vessel. 



The abdomen is now pointed at the extremity and divided into the 

 rudiments of the two anal stylets, which form large, acute tubercles, 

 llie yolk mass is now almost entirely enclosed within the body Avails, 

 forming an oval mass. 



Another embryo, observed July 27th, had reached about the same 

 stage of growth. Tlie pi'ocephalic lobe, including the antennary seg- 

 ment, is farther advanced than before. The entire head is divided 

 into two very distinct regions; i. e., one before the mouth-opening 

 (the pre-oral region, including the ocellnrij, or first and second seg- 

 ments; the ophthalmic, or third segment, and antennary, or fourth 

 segment of the headj ; and the other behind the mouth, (posl-oral, con- 

 sisting of the mandibular, or fifth segment, tha fr^t maxillary, or sixth 

 segment, and the second maxillarij, or labial, being the seventh and 

 last cephalic arthromere).* 



G. At this stage, the embryo is quite fully formed, and is about 

 ready to leave the egg. Tlie three regions of the body are now dis- 

 tinct. The articulations of the tergum are present, the yolk mass 

 being completely enclosed by the dorsal walls. The ventral ganglia 

 are fully formed and are seen laterally to be scjuare, with the stpiare 

 ends opposed, though the commissures cannot be distinguished. jMore 

 careful observation will undoubtedly reveal their presence. The 



* These observations confirm our theory of the number of segments composing 

 the head of insects as given in these Proceedings, Vol. x, p. 288. Readers will, how- 

 ever, please dele lines 11—14, and 25 on p. 289, as the succession of appendages there 

 given is now believed by the author to be erroneous. 



