108 University of California Publications in Zoology [VOL. 13 



4. A rich fibrillar supply is also described for the walls of the rec- 

 tum and for the region of the bases of the spines. One or more of 

 these fibrillae are described as extending down into each spine as a 

 sort of axial rod. 



A fibrillar layer is present in the internal wall of the rectal sheath 

 of Diplodinium ecaudatum, as has been described in the body of my 

 paper, but as was there pointed out, these rectal fibrillae (rect. f., pi. 

 3, fig. 3), are, in the ontogeny of D. ecaudatum, derived from the 

 ventral edge of the preexisting oesophageal wall and are not exactly 

 comparable to the "quere Fibrillenziige " described for the correspond- 

 ing region in Ophryoscolex purkynjei. These rectal fibers, however, 

 as well as those fibers in that portion of the oesophageal wall which I 

 have described as lying so close to the boundary layer, in the posterior 

 end of the animal, as to defy microscopic separation from the boundary 

 layer, are undoubtedly the homologues of the "Fibrillen" described 

 by Braune for the corresponding region in 0. Purkynjei. Other than 

 this no general fibrillation corresponding to that described for 0. Pur- 

 kynjei has been discovered in the forms investigated by me. 



In regard to the function of this "Fibrillenreichtum," Braune 

 concludes, "daB die Fibrillen keine Myoneme, sondern einfache elas- 

 tische Stabchen sind, denen nur die Stiitzfunktion zukommt." And 

 further he suggests that the retraction of the peristome and the mem- 

 branelle zones is easily brought into harmony with his view. To quote 

 again (p. 161), "Das Protoplasma bleibt nach wie vor ein scheinbar 

 homogenes, zahlfliissiges Medium, daB bei unseren Formen durch die 

 Fibrillenanhaufungen an eine starre Gestalt gebunden wird. Ver- 

 moge der Elastizitat der einzelnen Fibrillen ist das Protoplasma im- 

 stande, irgendwelche Reize durch schwache Lageveranderung der 

 beiden Wimperzonen zu beantworten. 



Aus dem Gesagten geht hervor, dass die bi- 

 zarre Korpergestalt der Ophryoscoleciden nur 

 durch das Fibrillensystem erhalten wird.' 



The arguments against the neuromotor apparatus of D. ecaudatum 

 serving merely as a supporting structure, the interpretation which 

 Braune places upon the "Fibrillenapparat" of 0. purkynjei, have been 

 given rather fully in my paper. It is unfortunate indeed that no 

 microphotographs accompany Braune 's article and that his drawings 

 are so fragmentary. As neither his description nor his figures give 

 any evidence that he saw the motor mass which shows so clearly in 

 microphotographs of D. ecaudatum (pi. 6, figs. 15, 16; pi. 7, figs, 22, 

 23, 33), it would seem either that a homologous structure is lacking in 



