Hagon.] 372 [January 22, 



ing to twenty-one, thougli often there are bnt ten abdominal rings. 

 Tlie embryo of Diplax in this respect presents more degradational 

 characters than the embryo of Phryganea, desciibed by Zaddach, 

 where the abdomen consists of but ten segments. 



No sexual oi'gans were observed in the embryo, or young larva, 

 though they may yet be discovered on more careful examination. 



Mr. S. H. Scuclder compared the symmetry of the fore 

 and hind parts of these embryos with that of the embryos 

 of vertebrates, recently described before the Society by the 

 President. This symmetry was jDroduced in the two groups 

 in diametrically opposite ways. In vertebrates, the different 

 parts develop gradually from the centre toward the two 

 extremities ; in articulates, the succession of growth is fi'om 

 the extremities toward the centre. 



On Lachlaxia abnormis, a new Genus and Species from 

 Cuba belonging to the Ephemerina. By Dr. H. Hagen. 



. In a very excellent collection of insects from Cuba received by the 

 Museum of Comparative Zoology from Mr. Wright, in the winter of 

 1867-1868, I found six female imagos of an Ephemerideous insect. 

 Wlien I first saw them, their habitus induced me to suppose that the 

 insect belonged to the most abnormal Ephemerideous genus Olir/oneu- 

 ria Pictet. This genus is very remarkable for the abortive condition 

 of the legs, these organs being so greatly atrophied, that they must 

 be nearly useless for the purpose of locomotion ; remarkable also for 

 the strength of the few longitudinal veins in the wings, and the rarity 

 of transverse veinlets, which exist only near the anterior margin of 

 the fore wings ; remarkable also for the very singular appendage at the 

 base of the fore wing, lodged below the heart-shaped ajjex of the meso- 

 thorax; remarkable finally for the curious strength of the junction of 

 the fore and hind wings, which has induced such excellent Entomol- 



or pedicel of the second maxillae, or labium, the expanded terminal portion being 

 drawn separately; d and a, two movable stout styles representing, perhaps, the 

 labial palpi; the lobe to which they are attached is multidentate, and adapted for 

 seizing its prey; on the right side the two styles are appressed to the lobe, x, 

 represents, perhaps, the ligula : but we have not yet studied its homologies care 

 fully; this part is attached to a transversely linear piece soldered to the main part 

 of the labium, i/, the 11th abdoniiual tergite, with its pair of conical anal styles. 

 z, the last tar.<al joint and pair of long slender claws. All the drawings in this 

 article, except Figure 6, were made from nature and put on wood by Sir. J. H. 

 Emerton of Salem, to whom I am indebted for many facts noticed and communi- 

 cated to me while making these drawings. 



