24 InBecta. 



ding from the testes, and (II) the azygotic portion, i. e. the doubled tube, 

 invaginated into itself and continuous at its other end with the body-wall. The 

 first part of the azygotic portion is a long slender tube (stenazygos), and the 

 second part is the broader eurazygos. The greater part of the eurazygos is ex- 

 ternal, forming the outer, or phallic portion of the doubled tube, but a part of it 

 may be internal and is then called the internal sac: this is not always present, 

 for in some forms the tube continues as the narrow stenazygos to the extremity 

 of the invaginated portion. The internal sac is, in all observed cases, everted 

 during copulation. The hard sclerites on the outer or phallic part of the tube 

 form two groups, a distal group (furthest from the body-wall) termed the me- 

 dian lobe, and a proximal group termed the tegmen: between median lobe 

 and tegmen, and between tegmen and body-wall, are the first and second 

 connecting membranes. The orifice at the point where the tube is invaginated 

 into itself is termed median orifice, while tegmen and median lobe together 

 are termed aedeagus (pp. 600 — 604). 



The writers next describe (pp. 605 — 609) some of the forms which the 

 parts assume. The median lobe in the more generalised forms is tubulär, with 

 the median orifice at its distal extremity. It may be articulated by a condyle to 

 the lateral lobes of the tegmen, in which case the first connecting membrane is 

 very short, or that membrane may be long, so that the median lobe has much 

 free play through the tegmen (Cucujoidea, Phytophagoidea). It may be reduced 

 in chitinisation and entirely enveloped by the tegmen (many Scarabaeoidea) : its 

 maximum reduction is reached in the Tenebrionid type, in which it is represented 

 only by a small membrane. The tegmen in the more generalised groups consists 

 of a basal piece and two lateral lobes, varying in form very greatly. The 

 basal piece may be chitinised so as to form a complete tube, or may form only 

 a ventral chitinous shield, while the dorsal part remains membranous: in Staphy- 

 linidae it is not chitinised at all, but remains entirely membranous. The lateral 

 lobes may remain separate, or be partly conjoined either dorsally or ventrally, 

 or by transverse extension may form a complete tubulär sheath. The internal 

 sac differs immensely, not only in different groups but even in allied species. 

 It may be excessively large and produced into long diverticula (Scarabaeoidea). 

 It may possess an armature of chitinous plates set with spines, etc. In some forms 

 it is permanently everted, a condition which appears in several different families. 

 In other cases it is produced into a long slender flagellum, sometimes of extreme 

 length and fineness, along which the stenazygos runs to its tip: this flagellum 

 also appears in several widely-separated families. 



Function. On this head there is but little Information, for the following 

 reason: that, since during copulation the sexual structures of c? and $ function 

 as a Single organ, a correlative knowledge of the $ genital tube is absolutely 

 necessary, but is lacking. No positive answer can yet be given to the question, 

 whether the c? organs actually place the sperm in the spermatheca of the $, or 

 in some other part of the ? tube. The authors incline to the opinion, that in many 

 cases at any rate, the J" organs actually reach the spermatheca, instancing the 

 flagellum as a structure highly adapted for this purpose. The importance of the 

 internal sac and its evagination during copulation are attested not only by some 

 direct observations, but by the arniatures etc. sometimes present on the sac. Its 

 eversion is effected, at least in part, by blood-pressure, and its invagination by 

 niuscular contraction. In some forms the median lobe is specially contrived to 

 effect the necessary blood-pressure (p. 611). The basally-directed spines and 

 hairs often present on the sac serve to prevent its being withdrawn from the ? 



