On the Structure and Affinities of Mnestra parasites Krolin etc. 6 1 



Fig. 14. Portion of umbral niargio, shüwing a well developed tentacle bearing 

 cnidopliurs, veliuu {r], radial canal {r.c) and cnidact icn]. 



Fig. 15. A siiuilar view sliowing a reduced tentacle withont cnidopliors. 



Fig. IG. Drawing of a bit of a tentacle partly in optical section to show its 

 structure. The endoderm cells are laden with large brownish-yellow 

 drops. 



Fig. n. Drawings of cnidophors. 



a. Surface view. 



b. In longitudinal optical section. 

 c, d. In transverse optical section. 



e, f. Contracted stalks of cnidophors. 



The nianubrium of Mnestra inserted into the body wall of Phyllirho'c. 



Trans verse section across distal end of manubrium. 



Endodermal lining of stomach. 



Epithelial lining at junction of a radial canal and the stomach. In 



living specimens currents indicated the exiatence of vibratile processes 



upon this eplthelium, probably as shown in Fig. 23. 



Portion of a radial canal. 



Endodermal lining of cavity at base of a tentacle. 



Longitudinal section througli a reduced tentacle showing the closely 



packed endoderm cells. Compare with Fig. 16. The circular canal 



C.C is shown in transverse section. 

 Figs. 25—35 are all drawings of cells contained within the meshes of the con- 



nective tissue of Phyllirhoe to which Mnestra were or had been once 



attached. The structures in question have not been observed in 



Phyllirhoe which had never been infested by a Mnestra, and they are 



believed to be the sexual cells and developing young of the Mnestra 



which have wandered into the Phyllirhoe. 

 Fig. 25. "Spermatozoa" of Mnestra clustered near a muscle fibre of Phyllirhoe. 



Two "ova" are shown in this preparation. 

 Fig. 26 a, b. "Ova" of Mnestra, one is attached to a muscle cell of Pliyllirhoe. 

 Fig. 27. 2-cell stage "embryo" of Mnestra. 

 Fig. 28. 4-cell stage "erabryo" of Mnestra. 

 Fig. 29, 30. 8-cell stage "embryos" of Mnestra lying among the connective 



tissue of the Pliyllirhoe. 

 Fig. 31, 32. lü-cell stage "embryos'' of Mnestra. 

 Fig. 33—35. Older "embryoes" of Mnestra. 

 Fig. 36—42. To illustrate individuai variations. Except Fig. 41 all are viewed 



from the oral surface, and tiie mouth and the subumbrella are turned 



towards the spectator. 



Colours. Red: gastro-vascular system. Blue: cnidacts and cnido- 



blast ring near the circular canal. 

 Fig. 36. After Claus' original drawing to show the marginal notch of Claus. 

 Fig. 37. After Müller & Gegenbaur. 

 Fig. 38. After an unpublished drawing by Prof. E. E. Lankester made at 



Naples, to show the quadriradial symmetry which was also characte- 



ristic of the Mnestra figured by Müller & Gegenbaur. 

 Fig. 39. One radial canal (IV) does not reach the central gastric cavity. Ten- 



tacles all reduced. 



