THE COPULATORY ORGANS OF INSECTS. 373 



not unite together to form a single piece grooved below, as 

 in the hymenopterous sting or ovipositor. And observations 

 which I have made on the development of the gonapophyses 

 of JBlatta lead me to the conclusion that the posterior bifid 

 pair are developed from the ninth and the anterior curved 

 pair from the eighth somite. In this case the latter will be 

 the homologue of the lances of the Bee-sting. 



Thus it would appear that, while there can be no doubt as 

 to the general unity of plan of ovipositors and stings, the 

 view of Lacaze-Duthiers must be modified. It must be ad- 

 mitted that these apparatuses appertain to the eighth and 

 ninth somites, and not to the ninth alone ; and that there is 

 much reason to suspect that their chief constituent parts are 

 modified limbs. 



The male copulatory organs ' are often very complicated, 

 and their homologies have not yet been fully determined. 

 Kraepelin (/. c), who has examined the development of these 

 parts in the Drone, and the modifications found in hermaphro- 

 dite Bees, is led to the conclusion that they are developed 

 from the eighth and ninth somites of the abdomen, and there- 

 fore are the homologues of the parts of the sting in the fe- 

 male. In the male JBlatta, however, it is obvious that the 

 male copulatory apparatus belongs to a more posterior somite 

 than that upon which the female gonapophyses are developed. 



The heart usually has the form of a flattened tube, closed at 

 its posterior end, but, in front, continued into the aorta, which 

 may be traced as far as the cerebral ganglia, and appears to 

 give off no branches. The sides of the tube present slit-like 

 openings (ostia), which vary in number from two to nine pairs ; 

 and, when there are several pairs, each pair answers to a so- 

 mite of the abdomen. The margins of the ostia may be sim- 

 ple, or may be produced inward into folds, which play the part 

 of valves. Muscular or ligamentous fibres may extend from 

 the hypodermis to the dorsal aspect of the heart, and serve to 

 suspend it in place. 



The alary muscles, which in most insects are fan-shaped, 

 and lie in pairs, opposite one another, on each side of the 

 heart, either unite in the middle line, or are inserted into a 

 sort of fascia, on the sternal aspect of the heart, to which 

 organ they are not directly attached. 



1 The male Libellulidce possess a peculiar copulatory apparatus developed 

 upon the sternum of the second abdominal somite. The genital aperture has 

 the ordinary position, and hence, before copulation, the male has to bend the 

 extremity of his abdomen upward in order to load this apparatus with sperma- 

 tozoa. 



