186 MR W. E. HOYLE ON 



which contains the " Chitinzapfen " of Leuckart (fig. 10, c.z). This is a 

 cylindrical body, pointed at its free extremity, and for the greater part of its 

 length attached by one side to the interior of the cavity in which it lies 

 (fig. 12, c.z) ; this cavity is only just large enough to contain the organ, whence 

 in section its lumen appears as a slit almost annular in form. Between this 

 part of the cell-mass and that which contains the vas deferens there is very 

 often a fenestra, as in the case shown in the drawing. 



With respect to the structure of this portion of the cirrus sac, it consists in 

 the main of small (0-002-0-005 mm.) nucleated cells, closely packed. In the 

 " Chitinzapfen " these show a tendency to a radial arrangement, and often leave 

 in the centre an irregular gap, which does not seem, however, to be of any 

 morphological signification. 



The epithelial lining of the vas deferens here assumes a most distinctly 

 radial arrangement (fig. 12, v.d), the cells being very long and slender, and 

 with nuclei either at one extremity or the other, rarely in the middle ; exter- 

 nally to this is a thinner layer of cells, which is an extension of the common 

 wall of the cirrus-sac. 



Of the cirrus itself I could find no trace whatsoever, and am consequently 

 led to imagine that it has not yet made its appearance ; if this be so, we have 

 here another point in which this animal corresponds with a very early stage of 

 L. tcenioides. It is possible, however, that in this species no cirrus is ever 

 formed, and that the " Chitinzapfen " does duty as a copulatory organ ; in any 

 case, I should be disposed to regard this as a kind of dilator for opening up the 

 sexual canal, either for the immediate flow of the semen, or as a preparation 

 for the passage of the slender cirrus, which by itself would hardly seem to be 

 fitted for such a purpose. In this process a very important service would be 

 rendered by the muscles which pass transversely across the sides of the cirrus 

 sac, for they would approximate the " Chitinzapfen " to the sexual orifice. 



The Accessory Gland (PI. XXVIII. fig. 13), above alluded to, is a flattened 

 mass of cells lying beside the intestine about the spot where the oesophagus 

 enters it, and stretching in a dorsal direction as far as the hook-gland. The 

 duct passes upwards and forwards through the middle of it, and is surrounded 

 by a space, crossed by numerous fine threads which are probably minute rami- 

 fications of the duct, although it could not be made out witli certainty that they 

 were hollow. At the extremities of these are groups of cells (0*008-0-014 mm. 

 in diameter), rendered polyhedral by mutual pressure, and provided with 

 relatively large nuclei, in some of the larger cells 0'008 mm. in diameter. 



As to the secretion of this gland and its function, I have been able to make 

 no observations. 



