1"JS 



COMPARATIVE ANATOMY. 



into the cavity of the ovarian tubes, and from it to the efferent 

 duct, which is provided with a considerable enlargement (it) (uterus). 

 A narrow coiled continuation of this leads to the protractile ovipositor 



(op). In the male there is a 

 circular canal, a portion only 

 of which forms the testis, 

 instead of the ovarian ring 

 (Fig. 156, a, t); the two 

 ends of the testis pass into 

 the efferent duct (vd) which 

 completes the ring. These 

 unite into a closely-coiled 

 portion, from which a 

 widened canal 

 vesicle arises - 

 similar to the 

 and, like it, protractile ; 

 the penis is attached to it. 

 Two large tufts of acces- 

 sory glands (gi) are con- 

 nected with the ends of the 



Fig. 156 

 opilio. 



or seminal 



- an organ 



ovipositor, 



Phalangium 



Vas 



Generative organs 



A Male organs. t 

 deferens, p Penis, to Retractors of penis. 

 gi Appended glands (after Krohn). B Female 

 organs, o Ovary. it Uterus, op Ovipositor. 



to Retractors of ovipositor. 



penis. 



The circular form of 

 germinal gland is still retained, in its completeness, in many of 

 the Acarina. In the female apparatus the greater part of the ring 

 is converted into the efferent organ, owing to the limitation of 

 the ova-producing part to a small division of it. This is most 

 marked in Pentastomum, where the ovary is attached to a circular 

 canal. The ovary is here differentiated from the canal. The part 

 of the ring, which forms the efferent ducts and passes into the 

 single portion, is often widened out into a uterus ; or the uterus 

 is formed by the unpaired portion alone. This is the casein Pentas- 

 tomum, the uterus of which forms a coiled canal of some length. 

 The unpaired portion of the efferent duct is generally much shortened 

 in the male, and the two parts of the rings connected with it are 

 widened out into seminal vesicles. Appended glands are connected 

 with the unpaired portion in both sexes. The great differences in the 

 distribution of the functions of parts of this canal lead to the separa- 

 tion of the ring into two genital tubes, the middle of the germ- 

 producing portion of the ring becoming sterile. The two halves of 

 the ring are then distributed to the sides, although in some cases 

 they are still connected by a canal, or by indifferent tissue; this 

 gives rise to organs which are only united at their orifices, or along 

 an unpaired portion connected with them (Ixodes). 



The hermaphrodite generative organs of the Tardigrada are 

 altogether unlike these arrangements. They consist of an unpaired 

 ovary and two testes which lie beside the enteron : their efferent 

 ducts pass into a receptaculum seminis, and open, generally provided 

 with special glands, into the cloaca. 



