THE ANATOMY OF PENTASTOMUM TERETigSOULUM. 71 



Fig. 53. — Transverse section across the central nerve mass of a young 

 male. The clear division into two halves is shown, and also the arrangement 

 of the fibres on the inside, and the ganglion-cells on the outside and up the 

 median line. 



Fig. 54.— Longitudinal section through a portion of the reproductive organs 

 of a mature female. The section is slightly oblique, so that it passes through 

 the commencement of the uterus and the union with this of one of the sperma- 

 thecal ducts. It passes also through one of the tubular accessory glands, 

 which curves in such a way that one side of the lips at its opening as well as 

 the gland itself is cut through. The layer of gland-cells around the sperma- 

 thecal duct is seen, and the muscle-fibres passing forwards from the common 

 part of the oviducts to the dorsal wall of the uterus. The latter is lined by 

 very definite columnar cells, and has internally a chitinous lining thrown 

 into distinct ridges. The chitinous lining becomes very thin in the sperm a- 

 thecal tube. Zeiss, F, oc. 4. 



Fig, 55. — Section across the wall of one of the spermathecae in a mature 

 female. Externally lies the layer of muscle-fibres. The epithelial cells are 

 distinct aad columnar, with somewhat tapering external ends embedded in a 

 granular material. Internally they iiave a thin cuticular lining. Zeiss, F, oc. 4. 



Fig. 56. — Oblique and transverse sections across the oviduct of a female, 

 the spermathecse of which contain spermatozoa, but in which no shells are 

 formed around the ova. Zeiss, camera, C, oc. 2. 



Fig. 57. — Oblique section of a portion of the ovary in a small immature 

 female, in which no spermatozoa are present in the spermatheca or vagina. 

 Both the upper and lower walls have the same structure. Zeiss, F, oc. 4. 



Fig. 58. — Transverse section across the oviduct of the same female as that 

 of which the ovary is drawn in Fig. 57. 



Fig. 59. — Longitudinal section through the point of union of the raid- and 

 hind gut in a young female. The columnar epithelial cells of the hind gut 

 with their cuticular lining dip underneath the less columnar cells of the mid- 

 gut. Just where the two parts unite a small number of gland-cells are 

 present, embedded in connective tissue external to the muscle layers. Zeiss, 

 F, oc. 4. 



PLATE IX. 



List of Refereneei. 



A. Nerve commissure. C. Cirrus. C. B. Cirrus bulb. Co. Tube leading 

 down to atrium genitale. C. S. Cirrus-sac. Ct. Connective tissue. Cu' . 

 Cuticle covering muscular mass in dilator rod-sac. Cu. C. B. Cuticle lining 

 central cavity of cirrus bulb. D. E. Epithelium lining dilator rod-sac. D. R- 

 Dilator rod. D. R. S. Dilator rod-sac. E^, 2, 3. The three layers forming the 

 walls of the cirrus bulb. Gr. Groove on the inner face of the mass in the 



