1896.] ^^)* [Goddard. 



For convenience we shall term it the shield. When the penis is flexed, 

 the distal part is protected by the overlying hamules so that this sclerite 

 is the only portion exposed. The point of flexion is just proximad of it, 

 which accounts for its very limited extent on the ventral aspect. The 

 second sclerite (2) is narrower than the first, is irregularly ring-shaped 

 and lies just distad of the shield. We shall call this the ring. As will 

 be seen later, it encircles most but not all the divisions of the penis-tip. 

 Distad of the ring on the dorso-mesal line is a chitinized body (5), which 

 divides into slender, tapering horns ; it is recognizable by its honey- 

 yellow color and Ave shall call it the fork. Arising from nearly the 

 same place are two membranous lobes (4), with transverse rows of 

 closely set chitinous hairs. These may be contracted into roundish 

 masses which, because of the brown hair, seem on first appearance to be 

 chitinized. When extended, as in the plate, they appear bannerlike, 

 and we shall term them the banners. Near the base of each is a small 

 cluster of long, stout bristles. Laterad of the banners are two blunt 

 lobes (6), somewhat membranous proximally but strongly chitinized 

 toward their distal end. As these are in many species somewhat twisted, 

 we have termed them the twists. Pressure on the genital bladder causes 

 them to rotate laterad and ventrad ; they may possibly serve, therefore, 

 to retain the hold of the penis-tip within the vulva. Ventrad of all the 

 others lies a large, membranous lobe which somewhat resemliles the 

 shape of a monk's hood and which we have called the hood (3). With 

 a view to possible homologies it is well to note the relative position of 

 these sti'uctures. The penis viewed from the tip presents a depression 

 or pit guarded above by the fork, below by the hood, laterad by the 

 banners and these again are guarded laterad by the twists. The ring 

 lies entii'ely dorsad of the hood and does not encircle it. According to 

 Rathke, there is in i. (enea a minute opening at the penis-tip. 



In Diplax vidua, the ventral sclerite is deeply emarginate, and its 

 caudo-lateral angles are strongly chitinized. The hamules are small and 

 inconspicuous (Fig. 5, g). The basal portion is short and the two lobes 

 are of about equal length. The tip of the anterior lobe is strongly 

 chitinized and very markedly incurved. 



The last division of the penis consists of but one sclerite in addition 

 to the cluster of appendages at the tip. This sclerite is long on the dor- 

 sal and short on the ventral aspect, where its edges nearly but not quite 

 meet. Its general shape would seem to indicate that it is formed by the 

 fusion of the shield and ring ; moreover it bears a pair of short trans- 

 verse ridges which look like the indications of such fusion. But as the 

 sclerite encloses the hood as well as the other part of the penis-tip, it 

 seems probable that no part of it corresponds to the ring, but that this 

 sclerite is entirely wanting in the present specimen. The penis-tip is 

 divided into a dorsal and a ventral portion. The ventral part is a 

 rounded lobe, thickly beset with hairs ; the dorsal part forms a mem- 

 branous base from which arise three pairs of appendages. Beginning 



