THE SENSORY ORGANS OTOCYSTS. 



297 



for some time, and its connection with the sac becomes elongated 

 and tubular (B and 0). This appendage, which was described by 

 KOLLIKER and by GRENACHER, named KOLLIKER'S duct, seems at 

 first to communicate with 

 the exterior, but is said 

 later to become separated 

 from the surface and to m 



end blindly. Its interior ^^ ^ 3b *t. 



is lined with cilia directed 

 towards the aperture of 

 the otocyst which are in 

 constant undulating move- 

 ment. This appendage 

 is also found in the adult. 

 BALFOUR compares it with 

 the recessus vestibidi of the 

 Vertebrates, the blind 

 appendage of the primitive 

 auditory vesicle which re- 

 presents its former connec- 

 tion with the point of 

 invagination. 



In that part of the wall 

 of the auditory vesicle 

 which lies almost opposite 

 to the point at which 

 KOLLIKER'S duct enters, 

 the epithelial cells thicken 

 to form the crista acustica, 

 and it is here that the 

 secretion of the otolith 

 takes place (Fig. HI D). 



The further development 

 of the otocysts is brought 

 about by the differentiation 

 of the crista acustica which 

 extends far over the wall 

 of the vesicle. The cells 



of the crista acustica lengthen, the inner free ends developing a 

 number of fine hairs. In this way arise the sensory epithelia which 

 compose the auditory ridges described by KOWALEVSKY and 



Fig. 141. Sections through the funnel-region of 

 several advanced embryos of Loliyo vulgaris 

 (original). A-C, transverse sections, />, sagittal 

 section, somewhat diagrammatic. The yolk 

 lias been omitted. de, yolk-epithelium ; ect, 

 ectoderm ; ///''*. mcsoderin ; "?. otocyst ; tr, 

 funnel-folds. 



