80 



DR. P. E. BEDDARD ON THE 



groove only ; apical pit at extremity of scolex ; water-vascular 

 system of scolex an abundant network of small tubes. 

 Hab. Monitor niloticus. 



(2) D. expansa Perrier. 



Duthiersia expansa Perrier, Arch. Zool. Exp. 1873, p. 359. 



Scolex larger ; bothria opening bp continuous antero-lateral 

 groove and by separate 'posteriorly situated pore, being thus funnel- 

 shaped ; apical pit not present ; water -vascidar system of scolex a 

 less abundant network of larger tubes. 



Hab. Monitor bengalevsis and other Indian forms. 



It is quite possible that were these two species found in quite 

 different hosts (i. e. of different genera or families) they would be 

 placed in separate genera. The differences of the scolex are 

 obviously large and important as these differences go among the 

 Pseud ophyllidea. I do not, however, attempt this separation. 



In conclusion I desire to draw attention to a few minutiae in 

 the structure of the scolex of Duthiersia which have not been 

 dwelt upon by those who have already studied the structure of 

 this genus. The strobila near to the scolex is somewhat hour- 

 glass-shaped in section, having a dorsal and ventral depression, 

 and thus a bulging at the two sides ; this is more marked in 

 D.fimbriata than in the larger species. The medulla is separated 

 from the cortical layer by a sharply marked band of longitudinal 

 muscles which become frayed out and thus end — as a distinct and 

 circumscribed layer — at the junction with the scolex. This layer 

 is the same in both species. A transverse layer lying within this 

 is to be seen in longitudinal section, but does not form a con- 

 tinuous coating of muscular fibre : there is simply a slender 

 bundle of fibres at the posterior end of each segment. This layer 

 escaped my attention in D. expansa, where it cannot at any rate 

 be so obvious as in the other Duthiersia. This state of affairs 

 contrasts with what obtains in /Solenophorus, believed to be closely 

 allied to Duthiersia. In the former the longitudinal layer is very 

 much thicker and with more scattered and at the same time 

 larger fibres, and the extent of the medulla is reduced. In trans- 

 verse sections the strobila of Solenophorus contrasts with that of 

 Duthiersia by its stouter form and oval to circular outline. This 

 thickening of the muscular layer in Solenophorus is, no doubt, 

 connected with the strong muscular supply of the walls of the 

 bothrial tubes in this genus. But in Duthiersia, in transverse 

 section, a thinnish layer of fibres is seen to extend along the 

 projecting walls of the bothria and represents the constricting 

 muscles seen in Solenophorus, though diminished in importance. 

 Within the bothrial tubes of Solenophorus the hypodermic cells 

 (subcuticular layer) are covered by a structureless stained (by re- 

 agents) and slightly opaque cuticle, outside of which is a clearer 

 but still rather granular yellowish cuticle of chitinous appear- 

 ance, of which the outermost layer is stained by reagents. In 



