YI 



ANTENNATA— SEXUAL ORGANS 



485 



In rare oases [Scolopendra) we find an unpaired germ gland and an unpaired duct, 

 into whose end, however, paired accessory organs (glands, receptacula seminis, vesiculse 

 seminales) enter. 



The unpaired portion may arise in very various ways. 



A. In the male of certain Farficulidce {Dermaptera) the ducts unite 

 at one part of their course to form an unpaired sperm vesicle, from 

 which the two ducts again as vasa deferentia separately run towards 

 the two male genital apertures. One of these ducts, however, becomes 

 reduced (Fig. 344, B), while the other, as an unpaired ductus ejacula- 

 torius, runs from the sperm vesicle to the outer aperture. 



B. An unpaired invagination of the integument grows from without 

 to meet the two ducts, so that these open externally as through an 



w w 



Fig. bu.—A-F, Diagrammatic representation of the sexual apparatus of various Insects. 

 A-E, Male organs. F, Female apparatus. The parts proceeding from invagination of the outer 

 integument are indicated by thick "black lines. A, Ephemerid. B, Forficula auricularia. C, 

 Larva of Orthoptera. B, (Edipoda (belonging to the Amdiidie). E, Cetonia aurata (Coleoptera). 

 F, .ffisohna (Liidlulid) (after Palmen). 



unpaired terminal portion lined with a chitinous cuticle (Fig. 344, 

 C-F). The 2 ducts may open into the unpaired terminal section either 

 by two separate apertures or by a single aperture. This arrangement 

 is found in the Apterygota, also in the Libelhdidce, Plecoptera, Orthoptera, 

 Rhynchota, and perhaps in other orders as well. Paired or unpaired 

 accessory structures may appear in the terminal portion through 

 secondary invaginations. 



G. A second unpaired section is sometimes added to the unpaired 

 terminal portion described under B ; this section arises by the fusing 

 of the two sperm ducts or oviducts throughout tracts of varying length 

 to form one unpaired duct (ductus ejaculatorius, uterus, vagina, etc.), 

 this unpaired duct enters the ectodermal invagination. This is 

 probably the case in all the so-called higher insects (insects with com- 

 plete metamorphosis). 



The position of the outer genital apeptures is very various. 



In the Chilopoda among the Myriapoda the unpaired genital aperture 

 lies in the penultimate body segment, i.e. in the genital segment, whose 

 limbs may be transformed into genital appendages. 



