200 ISAO IIJIMA. 



be solid. Professor Lankester (No. 14, p. 313) regards the 

 tubular and the solid fibres, together with the hsematopho- 

 rous vessels, as three permauent varieties of the vaso-fibrous 

 tissue. He found a direct continuity between the first two 

 kinds of fibres and the third, which corresponds to what I 

 have seen. 



The black pigment granules (brown in Hirudo medici- 

 nalis), if the action of the acid has been weak, remain un- 

 coloured by carmine ; but in cases of strong action, or when 

 hardened in Kleinenberg's picro-sulphuric acid, there is no 

 trace of colour left, and the nuclei become very distinct. 

 These nuclei (ca. '004 mm. in diameter) were round or oval 

 in outline, and showed no nucleoli. The widest portion of 

 these fibres, which is always near the junction of some two 

 or three strands, measures about "015 mm. 



I am unable to offer any suggestion in regard to the 

 significance of these fibres. In the case of the medicinal 

 leech. Professor Lankester is inclined to think '■ that there 

 is actually a continual development of off-shoots of the 

 brown pigmented system of fibres into thin-walled hsemato- 

 ])liorous vessels, the nuclei entering the blood stream when 

 communication is once established, and the brown granular 

 wall becoming transparent and structureless by the absorp- 

 tion of its granules." Whether this view is applicable to 

 the ovarial system of Nephelis I am quite unable to say. 1 

 have thus far been unable to recognise any blood-vessels in 

 the ovary wall. 



It will aid in the further description of the ovary to intro- 

 duce here some explanatory remarks and definitions. As 

 the ovary- wall does not present complete uniformity, either 

 in thickness or in composition, in its entire circumference, 

 it Avill be necessary to distinguish between different sides by 

 the use of different terms. That side of the ovarial tube 

 which, at the fore end of the tube, always looks outward 

 towards the margin of the body, but which elsewhere may 

 face in any direction, may be called the radial side (ra. s., 

 fig. 2), since it is always thickened along its median line. 

 The longitudinally-thickened portion of the wall will be de- 

 signated as the rachis (ra., fig. 4, PL XVII). The opposite 

 side of the ovarial tube will be called the mediad side (m. s., 

 fig, S), although it cannot of course always lie nearest the 

 median line of the body. In fig. S, PI. XVI, the middle of 

 the rachal side is marked a, and the corresponding mediad 

 line by b. Although the position of these lines varies in 

 different parts of the ovaries, owing to the winding of the 

 tubes, they always preserve the same relation to each other. 



