TAPEWORM FEOM APEETYX. 95 



^.longitudinal excretory canal. The imbrication of the proglottids is well 

 seen. 



Fig. 14. — An onchosphere enclosed within its coats. 



Fig. 15.— The apex of the scolex, showing the retracted rostellar apparatus; 

 in optical section, from a transparent specimen. X 375. (Camera.) a. the 

 apical pore, R. rostellum, r. receptaculum rostelli, s. sucker. Compare the 

 size wit,h that of the apparatus of D. minuta (fig. 10). 



The Rostellum of Drepauidotaenia minuta. 



Figs. 16 — 18 are optical sections, from stained, transparent, entire stro- 

 bilas. All are drawn with th.e camera, under the same magnification. 

 X 875. 



Fig. 16. — The rostellum entirely withdrawn into the receptaculum. a. 

 Apical pore in the scolex. b. Acanthophore. c. Reservoir of rostel- 

 lum. d. The circular muscles of its wall (the longitudinal only 

 shown at the base), e. The radial muscles. m\ m". The extrinsic 

 muscles that move the receptaculum. p. Finely granular contents of 

 the anterior region of the receptacle, r. The muscular wall of the 

 receptacle. S. Outline of sucker, s. Coarsely granular contents of 

 the posterior region of the receptacle contained in membranous sacs. 

 10. The septum formed by apposition of these sacs. 



Fig. 17. — The rostellum at the commencement of protrusion. The 

 acanthophore is moving upwards in the pre-rostellar canal. The 

 reservoir is greatly constricted by the circular muscles at the neck 

 and elsewhere; the radial muscles (e.) are still horizontal. This pro- 

 trusion is effected by the contraction of the wall of the receptaculum ; 

 the "septum" (w.) between the membranous sacs is now longer, and 

 the sacs lie nearly entirely behind the rostellum. y. is a sphincter 

 muscle closing the lower aperture of the pre-rostellar canal. The 

 radial muscles, as well as other details, show better in this preparation, 

 which was stained in alum-cochineal (Czokor). The radials are appa- 

 rently interrupted by vertical lines ; as a fact, there are eighteen groups 

 of radial muscles. 



Fig. 18. — The rostellum is protruded, though not to its fullest extent. 

 The acanthophore not only projects through the aperture (a), but is 

 distended by the fluid contents of the reservoir, forced upwards by the 

 contraction of its wall. The longitudinal muscles are here siiowu. 

 The apex of the acanthophore is depressed {b'), and between the hooks 

 the "radial muscles" {e) are seen to be vertically disposed. 



Figs. 19 and 20 are longitudinal sections x 450. Outlines and main 

 details with camera. 



