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NEW YORK STATE MUSEUM 



But we are here concerned only with giving a simple ac- 

 count of what this accessory genital apparatus, developed upon 

 the 2d and 3d abdominal segments of the male, consists of, 

 and how it compares in different genera of dragon flies. As 

 already stated, the receptacle for the sperm is the vesicle, 

 situated at the front of the sternum of the 3d segment in the 

 median line, and visible externally as a rounded prominence. 

 The organ for the transference of the contents of the vesicle 

 to the bursa copulatrix of the female is a median, unpaired, 

 jointed and retractile intromittent organ, the penis. This is 

 situated directly in front of the vesicle, on the sternum of the 

 second segment, and is more or less directly connected with 

 the vesicle. Vesicle and penis are the direct agents of sperm 



Fig. 17 Male abdominal appendages of the dragon fly E don is helena Ndm. i, z, 

 3 the three basal abdominal segments and their appendages, inverted and viewed from the 

 side; v vesicle; gl genital lobe; h hamule; al anterior lamina, in both lateral and ventral 

 views; t tip of the abdomen less enlarged, segments 7 to lo, and appendages 



transference : but there are other parts accessory to their 

 function. Beside the penis are one or two pairs of hamules, 

 that assist in maintaining proper positions in copulation. 

 Before the penis there rises from the sternum of the 2d 

 segment a more or less prominent, chitinized, concave arching 

 plate, the sheath of the penis, doubtless with a protective 

 function. All these, and other parts yet to be mentioned, are 

 developments from the sternum : and in the family Libel- 

 lulidae, the tergum also contributes by the development of the 

 well known "genital lobes" from its posterolateral angles of the 

 2d segment. These parts are externally visible. Their general 

 appearance is shown in figure 5, in a case in which but a single pair 

 of hamules is developed. It will be seen that these parts cover only 

 the posterior part of the sternum of the 2d segment, and a bit of 

 the front of the sternum of the 3d segment. It was doubtless in 

 the hollow between these two segments, in the reentrant angle 



