OP OECANTHUS AND TELEAS. 255 



the mesodermic elements lying along the wall of the heart. In the enlarged portion of the 

 mass there appears a space comparatively free from germinal cells but filled with a finely 

 granular protoplasm ; in this area are to be seen a few nuclei — with peculiar bar-shaped 

 nucleoli — which are much larger, and also more sharply defined, than the nuclei of 

 the remaining germinal cells. These are the nuclei of the primitive ova and probably give 

 rise to all of the ovarian germs. At a later date each ovarian body is differentiated into 



fifteen or twenty ovarioles — which include the greater part of the cell mass and an 



oviduct which is formed as an out-growth from the hind end of the mass. The details of 

 the tubulation of the ovarian masses and the distribution of the germinal cells require fur- 

 ther study. 



At the time of revolution the appendages exhibit traces of their future subdivisions. 

 The antennae are about one half as long as the embryo and are comparatively thick. The 

 mandibles are much broadened and slightly trilobed. Both pairs of maxillae are distinctly 

 trilobed and are much longer than the mandibles. The three pairs of thoracic appendages 

 are of nearly equal length, but the third pair exceeds the other two in bulk. The basal 

 joints of all three pairs are considerably enlarged, but their tips are as yet rounded. Soon 

 after revolution they increase rapidly in length and become sharply bidentate. The first 

 pair of abdominal appendages have nearly disappeared, while the anal stylets, or last pair of 

 abdominal appendages, has grown to the length of the mandibles, and at the close of 

 embryonic life have acquired considerable size and are covered with hairs. 



After the yolk sac is formed a cuticula is secreted about the embryo, but it does not 

 quite reach to the edges of the yolk sac and is much thinner on the sides than on the ven- 

 tral surface of the embryo. This layer is soon cast off and a second one secreted. From 

 the latter are derived the thick chitinous parts of the mandible and maxillae, the onychia 

 and tibial spines of the legs, and the balloon shaped processes of the anal stylets. With the 

 growth of the embryo, the maxillary and mandibular regions of the body are oreatly short- 

 ened, their dorsal portions disappearing altogether and their ventral portions fusino- with 

 the oral region. Both pairs of maxillae become somewhat reduced in size and with the 

 mandibles completely cover the mouth opening. They are in turn covered by the broad 

 labrum, which has now been reduced to a thin chitinous flap. (PI. 19, figs. 7, 8 ; pi. 20 fio-s 

 45,46.) 



After the secretion of the second layer of cuticula the surface of the body is thickly 

 beset with bristly hairs. They are especially developed upon the antennae and anal sty- 

 lets. On the inner surfaces of the basal portions of the latter are seen two vesicular bodies 

 (pi. 19, figs. 14, 15, 16) which from their structure and position can be only modified hairs. 

 They appear after the first ecdysis and then only one upon each stylet. Subsequently 

 they increase in number, probably with each ecdysis, until in the adult insect one finds 

 on each from ten to fifteen such bodies. The cuticula at the base of the organ is raised up 

 in the form of a vase, from the depth of which the stem of the balloon takes its ori<rin. 

 The latter is filled with clear vesicular bodies during the period of embryonic life but 

 appears to be entirely empty in the adult. 1 At the time of hatching there are no traces 

 of wings, but later these appear jis flat outgrowths of the dorsal ectoderm and in the man- 



1 These organs may possibly be homologous to the sense pare Packard's description of those met with in Blatta. 

 organs found on the anal stylets of other Orthoptera. Com- Araer. Nat. vol. IV., p. 620. 



