82 The Form of Insects 



form of individual parts. The testis is sometimes a 

 simple tube, or consists of a number of branched 

 tubes. In most Moths and in some solitary Wasps 

 and other insects, the two testes are situated close 

 together and enclosed in a common membrane, so that 

 they seem to form a single, unpaired organ. The 

 numerous bushy utricles of the cockroach in which 

 the spermatozoa are stored and associated in bundles 

 preparatory to ejaculation, are represented in most 

 insects by a few long tubes — the accessory glands, in 

 which mucus is secreted or packets {spertnatophores) 

 for the sperm-cells are formed (2). 



Comparison of the male with the female repro- 

 ductive organs shows a general resemblance between 

 the two sexes. The ovaries and oviducts correspond 

 with the testes, sperm-tubes and sperm-vesicles ; while 

 the vagina is comparable to the sperm-duct, both 

 being lined with chitin and formed by inpushing of 

 the outer skin. In Mayflies the paired sperm-ducts 

 (yasa deferentia) open directly to the exterior ; while 

 in Earwigs, though the ends of these ducts usually 

 become fused, or one disappears so that there is a 

 single terminal duct, it has no chitinous lining (49). 



Male Genital Armature. — As in the female insect 

 certain hard chitinous processes at the hinder end of 

 the body form an ovipositor, so the male is provided 

 with a special armature for use in seizing his mate 

 and ensuring the introduction of sperm-cells into her 

 sperm-reservoir. The armature of the Cockroach is 

 concealed within the ninth sternite ; it consists of 

 a "titillator" — a long curved process with hollow 

 base and hooked tip, a solid " penis" clubbed at the 

 end, and a number of irregular hooks whose precise 

 functions have not been made out (fig. ^6) (l). 



In many insects paired processes connected with 

 the ninth segment, to which they are hinged, are 



