110 



A. G. Bourne — On cpiiaiit Eaiiliwonns from the 



[No. 1, 



There is still some doubt, I tliiiik, with regard to the position of 

 the septa in all species, and, until this is resolved, it is difficult to fix the 

 position of the testes, seminal reservoirs, and ciliated rosettes. Beddard 

 states that in T. gammi the two most anterior septa are septa IV — V 

 and V — VI ; that one septum, presumably VI — VII, is absent and that 

 " farther back are three' thickened septa which lie between segments 

 VIII, IX and X." Now, I believe, that in ascribing a position to the 

 internal organs we should determine the somite by the septa which 

 bound it. It is true that the septum often appears to have a position 

 which is not in accordatice with the limits of the somites as marked 

 externally, but this may be seen in longitudinal sections to be due 

 to the fact that the muscular fibres of the septum adhere for some 

 little distance, either backwards or forwards, to the body wall. Bed- 

 dard's statement that three septa lie between three " segments " is 

 misleading. Three septa bound two somites. I would interpret the 

 " three thickened septa " mentioned above as septa VIII — IX, IX — X, 

 and X — XI. If this be the case the single pair of testes and ciliated 

 rosettes lie in somite XI. According to Beddard's account of T. gammi 

 they lie in somite X, while judging from his figure they would appear to 

 be in somite XII. 



I propose to define the present species as follows : — 



T. masoni. — Penial setse of two varieties lying together in the same 

 sac ; the one variety very long, with a slight S-shaped curve and a sub- 

 terminal dilation at the distal extremity, while the proximal extre- 

 mity presents irregular transverse markings ; the other variety shorter, 

 somewhat spear-shaped, the distal extremity flattened and furnished 

 with obscurely marked chevron-shaped ridges. 



The setse in about the posterior third of the body are not arranged 

 in couples as in the anterior two-thirds, but are equi-distant from one 

 another, the ventral gap being slightly larger than the interspace 

 between any two setas. 



The spermathecaa are provided with two diverticula, the one bifid 

 the other obscurely trifid. 



1 do not suggest any modifications of Beddard's definition of the 

 genus, but expect that some will be ultimately necessary. As far as we 

 know, neither the character of the diverticula of the spermathecsB nor 

 the number of these organs themselves is of generic value. The number 

 of intestinal glands probably varies in different species, and, further, I am 

 not quite sure about the position of the testes. 



