1868.] 



365 



[Packard. 



Section of Entomology. January 22, 1868. 



Mr. L. Trouvelot in the chair. Fourteen members present. 



The following papers were read : — 



On the Development of a Dragon-fly (Diplax). By A. 

 S. Packard, Jr., M. D. 



1. In all the eggs observed, the blastoderm had been formed, and 

 consequently the nucleated blastodermic cells had disappeared, and, 

 at this stage, there was a clear space about what is probably the ante- 

 rior pole of the egg, where the head is eventually to be developed. 



2. In the next stage (Fig.l.) the head is partially sketched out, 

 with the rudiments of the limbs and mouth-parts; and the sternites, or 

 ventral walls, of the thorax and of 

 the two basal rings of the head ap- 

 pear. The anterior part of the head, 



including the so-called "procephalic / I ^^^^^^0M „ 

 lobe" overhangs and conceals the ' ''^^>^^;"^^^J5»^^". •^'^ 

 base of the antennae. It is probable 

 that more careful observation would 

 have shown the end of the abdomen 

 folded back upon the dorsal region, 

 as usual at this pei'iod in the em- j-j^ ^ 



bryos of the insects and crustaceans c-^ • e ^ ti „ „,^ 



•' . Side-view of embryo. The pro- 



whose embryology has been studied, cephalic lobe is not shown. 1, an- 



rr<i_ . T., 1 , tennEc; 2, mandibles; 3, maxillrc ; 



The antenna?, mandibles and max- 4^ second maxill.-c (labium); 5-7, 

 illae form a group by themselves, legs. These numbers and letters 

 , ., , 1 .11 / 1 are the same in all the figures, fhe 



while the second maxilljB (or la- under-side (sternum) of six seg- 

 bium) are very much larger and ments are indicated, 

 turned backwards, being temporarily 

 grouped with the legs. 1 . 



There are traces only of the two g'. 



basal sterna of the abdomen. This / y ,-^S^^ 



indicates that the basal abdominal *' 



segments grow in succession from g . 



the base of the abdomen, the middle 



ones appearing last. The post- 

 abdomen has probably been devel- c>>.vk/d 

 oped synchronous with the proceph- \ ^J' 

 alic lobe, as in all insect and crus- 

 tacean embryos yet observed. As 

 observed by Zaddach, these two Ventral view oAhe same. 



